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 """ Implementation of the trigsimp algorithm by Fu et al. The idea behind the ``fu`` algorithm is to use a sequence of rules, applied in what is heuristically known to be a smart order, to select a simpler expression that is equivalent to the input. There are transform rules in which a single rule is applied to the expression tree. The following are just mnemonic in nature; see the docstrings for examples. TR0 - simplify expression TR1 - sec-csc to cos-sin TR2 - tan-cot to sin-cos ratio TR2i - sin-cos ratio to tan TR3 - angle canonicalization TR4 - functions at special angles TR5 - powers of sin to powers of cos TR6 - powers of cos to powers of sin TR7 - reduce cos power (increase angle) TR8 - expand products of sin-cos to sums TR9 - contract sums of sin-cos to products TR10 - separate sin-cos arguments TR10i - collect sin-cos arguments TR11 - reduce double angles TR12 - separate tan arguments TR12i - collect tan arguments TR13 - expand product of tan-cot TRmorrie - prod(cos(x*2**i), (i, 0, k - 1)) -> sin(2**k*x)/(2**k*sin(x)) TR14 - factored powers of sin or cos to cos or sin power TR15 - negative powers of sin to cot power TR16 - negative powers of cos to tan power TR22 - tan-cot powers to negative powers of sec-csc functions TR111 - negative sin-cos-tan powers to csc-sec-cot There are 4 combination transforms (CTR1 - CTR4) in which a sequence of transformations are applied and the simplest expression is selected from a few options. Finally, there are the 2 rule lists (RL1 and RL2), which apply a sequence of transformations and combined transformations, and the ``fu`` algorithm itself, which applies rules and rule lists and selects the best expressions. There is also a function ``L`` which counts the number of trigonometric functions that appear in the expression. Other than TR0, re-writing of expressions is not done by the transformations. e.g. TR10i finds pairs of terms in a sum that are in the form like ``cos(x)*cos(y) + sin(x)*sin(y)``. Such expression are targeted in a bottom-up traversal of the expression, but no manipulation to make them appear is attempted. For example, Set-up for examples below: >>> from sympy.simplify.fu import fu, L, TR9, TR10i, TR11 >>> from sympy import factor, sin, cos, powsimp >>> from sympy.abc import x, y, z, a >>> from time import time >>> eq = cos(x + y)/cos(x) >>> TR10i(eq.expand(trig=True)) -sin(x)*sin(y)/cos(x) + cos(y) If the expression is put in "normal" form (with a common denominator) then the transformation is successful: >>> TR10i(_.normal()) cos(x + y)/cos(x) TR11's behavior is similar. It rewrites double angles as smaller angles but doesn't do any simplification of the result. >>> TR11(sin(2)**a*cos(1)**(-a), 1) (2*sin(1)*cos(1))**a*cos(1)**(-a) >>> powsimp(_) (2*sin(1))**a The temptation is to try make these TR rules "smarter" but that should really be done at a higher level; the TR rules should try maintain the "do one thing well" principle. There is one exception, however. In TR10i and TR9 terms are recognized even when they are each multiplied by a common factor: >>> fu(a*cos(x)*cos(y) + a*sin(x)*sin(y)) a*cos(x - y) Factoring with ``factor_terms`` is used but it it "JIT"-like, being delayed until it is deemed necessary. Furthermore, if the factoring does not help with the simplification, it is not retained, so ``a*cos(x)*cos(y) + a*sin(x)*sin(z)`` does not become the factored (but unsimplified in the trigonometric sense) expression: >>> fu(a*cos(x)*cos(y) + a*sin(x)*sin(z)) a*sin(x)*sin(z) + a*cos(x)*cos(y) In some cases factoring might be a good idea, but the user is left to make that decision. For example: >>> expr=((15*sin(2*x) + 19*sin(x + y) + 17*sin(x + z) + 19*cos(x - z) + ... 25)*(20*sin(2*x) + 15*sin(x + y) + sin(y + z) + 14*cos(x - z) + ... 14*cos(y - z))*(9*sin(2*y) + 12*sin(y + z) + 10*cos(x - y) + 2*cos(y - ... z) + 18)).expand(trig=True).expand() In the expanded state, there are nearly 1000 trig functions: >>> L(expr) 932 If the expression where factored first, this would take time but the resulting expression would be transformed very quickly: >>> def clock(f, n=2): ... t=time(); f(); return round(time()-t, n) ... >>> clock(lambda: factor(expr)) # doctest: +SKIP 0.86 >>> clock(lambda: TR10i(expr), 3) # doctest: +SKIP 0.016 If the unexpanded expression is used, the transformation takes longer but not as long as it took to factor it and then transform it: >>> clock(lambda: TR10i(expr), 2) # doctest: +SKIP 0.28 So neither expansion nor factoring is used in ``TR10i``: if the expression is already factored (or partially factored) then expansion with ``trig=True`` would destroy what is already known and take longer; if the expression is expanded, factoring may take longer than simply applying the transformation itself. Although the algorithms should be canonical, always giving the same result, they may not yield the best result. This, in general, is the nature of simplification where searching all possible transformation paths is very expensive. Here is a simple example. There are 6 terms in the following sum: >>> expr = (sin(x)**2*cos(y)*cos(z) + sin(x)*sin(y)*cos(x)*cos(z) + ... sin(x)*sin(z)*cos(x)*cos(y) + sin(y)*sin(z)*cos(x)**2 + sin(y)*sin(z) + ... cos(y)*cos(z)) >>> args = expr.args Serendipitously, fu gives the best result: >>> fu(expr) 3*cos(y - z)/2 - cos(2*x + y + z)/2 But if different terms were combined, a less-optimal result might be obtained, requiring some additional work to get better simplification, but still less than optimal. The following shows an alternative form of ``expr`` that resists optimal simplification once a given step is taken since it leads to a dead end: >>> TR9(-cos(x)**2*cos(y + z) + 3*cos(y - z)/2 + ... cos(y + z)/2 + cos(-2*x + y + z)/4 - cos(2*x + y + z)/4) sin(2*x)*sin(y + z)/2 - cos(x)**2*cos(y + z) + 3*cos(y - z)/2 + cos(y + z)/2 Here is a smaller expression that exhibits the same behavior: >>> a = sin(x)*sin(z)*cos(x)*cos(y) + sin(x)*sin(y)*cos(x)*cos(z) >>> TR10i(a) sin(x)*sin(y + z)*cos(x) >>> newa = _ >>> TR10i(expr - a) # this combines two more of the remaining terms sin(x)**2*cos(y)*cos(z) + sin(y)*sin(z)*cos(x)**2 + cos(y - z) >>> TR10i(_ + newa) == _ + newa # but now there is no more simplification True Without getting lucky or trying all possible pairings of arguments, the final result may be less than optimal and impossible to find without better heuristics or brute force trial of all possibilities. Notes ===== This work was started by Dimitar Vlahovski at the Technological School "Electronic systems" (30.11.2011). References ========== Fu, Hongguang, Xiuqin Zhong, and Zhenbing Zeng. "Automated and readable simplification of trigonometric expressions." Mathematical and computer modelling 44.11 (2006): 1169-1177. http://rfdz.ph-noe.ac.at/fileadmin/Mathematik_Uploads/ACDCA/DESTIME2006/DES_contribs/Fu/simplification.pdf http://www.sosmath.com/trig/Trig5/trig5/pdf/pdf.html gives a formula sheet. """ from __future__ import print_function, division from collections import defaultdict from sympy.simplify.simplify import bottom_up from sympy.core.sympify import sympify from sympy.functions.elementary.trigonometric import ( cos, sin, tan, cot, sec, csc, sqrt, TrigonometricFunction) from sympy.functions.elementary.hyperbolic import ( cosh, sinh, tanh, coth, sech, csch, HyperbolicFunction) from sympy.functions.combinatorial.factorials import binomial from sympy.core.compatibility import ordered, range from sympy.core.expr import Expr from sympy.core.mul import Mul from sympy.core.power import Pow from sympy.core.function import expand_mul from sympy.core.add import Add from sympy.core.symbol import Dummy from sympy.core.exprtools import Factors, gcd_terms, factor_terms from sympy.core.basic import S from sympy.core.numbers import pi, I from sympy.strategies.tree import greedy from sympy.strategies.core import identity, debug from sympy.polys.polytools import factor from sympy.ntheory.factor_ import perfect_power from sympy import SYMPY_DEBUG # ================== Fu-like tools =========================== def TR0(rv): """Simplification of rational polynomials, trying to simplify the expression, e.g. combine things like 3*x + 2*x, etc.... """ # although it would be nice to use cancel, it doesn't work # with noncommutatives return rv.normal().factor().expand() def TR1(rv): """Replace sec, csc with 1/cos, 1/sin Examples ======== >>> from sympy.simplify.fu import TR1, sec, csc >>> from sympy.abc import x >>> TR1(2*csc(x) + sec(x)) 1/cos(x) + 2/sin(x) """ def f(rv): if isinstance(rv, sec): a = rv.args[0] return S.One/cos(a) elif isinstance(rv, csc): a = rv.args[0] return S.One/sin(a) return rv return bottom_up(rv, f) def TR2(rv): """Replace tan and cot with sin/cos and cos/sin Examples ======== >>> from sympy.simplify.fu import TR2 >>> from sympy.abc import x >>> from sympy import tan, cot, sin, cos >>> TR2(tan(x)) sin(x)/cos(x) >>> TR2(cot(x)) cos(x)/sin(x) >>> TR2(tan(tan(x) - sin(x)/cos(x))) 0 """ def f(rv): if isinstance(rv, tan): a = rv.args[0] return sin(a)/cos(a) elif isinstance(rv, cot): a = rv.args[0] return cos(a)/sin(a) return rv return bottom_up(rv, f) def TR2i(rv, half=False): """Converts ratios involving sin and cos as follows:: sin(x)/cos(x) -> tan(x) sin(x)/(cos(x) + 1) -> tan(x/2) if half=True Examples ======== >>> from sympy.simplify.fu import TR2i >>> from sympy.abc import x, a >>> from sympy import sin, cos >>> TR2i(sin(x)/cos(x)) tan(x) Powers of the numerator and denominator are also recognized >>> TR2i(sin(x)**2/(cos(x) + 1)**2, half=True) tan(x/2)**2 The transformation does not take place unless assumptions allow (i.e. the base must be positive or the exponent must be an integer for both numerator and denominator) >>> TR2i(sin(x)**a/(cos(x) + 1)**a) (cos(x) + 1)**(-a)*sin(x)**a """ def f(rv): if not rv.is_Mul: return rv n, d = rv.as_numer_denom() if n.is_Atom or d.is_Atom: return rv def ok(k, e): # initial filtering of factors return ( (e.is_integer or k.is_positive) and ( k.func in (sin, cos) or (half and k.is_Add and len(k.args) >= 2 and any(any(isinstance(ai, cos) or ai.is_Pow and ai.base is cos for ai in Mul.make_args(a)) for a in k.args)))) n = n.as_powers_dict() ndone = [(k, n.pop(k)) for k in list(n.keys()) if not ok(k, n[k])] if not n: return rv d = d.as_powers_dict() ddone = [(k, d.pop(k)) for k in list(d.keys()) if not ok(k, d[k])] if not d: return rv # factoring if necessary def factorize(d, ddone): newk = [] for k in d: if k.is_Add and len(k.args) > 1: knew = factor(k) if half else factor_terms(k) if knew != k: newk.append((k, knew)) if newk: for i, (k, knew) in enumerate(newk): del d[k] newk[i] = knew newk = Mul(*newk).as_powers_dict() for k in newk: v = d[k] + newk[k] if ok(k, v): d[k] = v else: ddone.append((k, v)) del newk factorize(n, ndone) factorize(d, ddone) # joining t = [] for k in n: if isinstance(k, sin): a = cos(k.args[0], evaluate=False) if a in d and d[a] == n[k]: t.append(tan(k.args[0])**n[k]) n[k] = d[a] = None elif half: a1 = 1 + a if a1 in d and d[a1] == n[k]: t.append((tan(k.args[0]/2))**n[k]) n[k] = d[a1] = None elif isinstance(k, cos): a = sin(k.args[0], evaluate=False) if a in d and d[a] == n[k]: t.append(tan(k.args[0])**-n[k]) n[k] = d[a] = None elif half and k.is_Add and k.args[0] is S.One and \ isinstance(k.args[1], cos): a = sin(k.args[1].args[0], evaluate=False) if a in d and d[a] == n[k] and (d[a].is_integer or \ a.is_positive): t.append(tan(a.args[0]/2)**-n[k]) n[k] = d[a] = None if t: rv = Mul(*(t + [b**e for b, e in n.items() if e]))/\ Mul(*[b**e for b, e in d.items() if e]) rv *= Mul(*[b**e for b, e in ndone])/Mul(*[b**e for b, e in ddone]) return rv return bottom_up(rv, f) def TR3(rv): """Induced formula: example sin(-a) = -sin(a) Examples ======== >>> from sympy.simplify.fu import TR3 >>> from sympy.abc import x, y >>> from sympy import pi >>> from sympy import cos >>> TR3(cos(y - x*(y - x))) cos(x*(x - y) + y) >>> cos(pi/2 + x) -sin(x) >>> cos(30*pi/2 + x) -cos(x) """ from sympy.simplify.simplify import signsimp # Negative argument (already automatic for funcs like sin(-x) -> -sin(x) # but more complicated expressions can use it, too). Also, trig angles # between pi/4 and pi/2 are not reduced to an angle between 0 and pi/4. # The following are automatically handled: # Argument of type: pi/2 +/- angle # Argument of type: pi +/- angle # Argument of type : 2k*pi +/- angle def f(rv): if not isinstance(rv, TrigonometricFunction): return rv rv = rv.func(signsimp(rv.args[0])) if not isinstance(rv, TrigonometricFunction): return rv if (rv.args[0] - S.Pi/4).is_positive is (S.Pi/2 - rv.args[0]).is_positive is True: fmap = {cos: sin, sin: cos, tan: cot, cot: tan, sec: csc, csc: sec} rv = fmap[rv.func](S.Pi/2 - rv.args[0]) return rv return bottom_up(rv, f) def TR4(rv): """Identify values of special angles. a= 0 pi/6 pi/4 pi/3 pi/2 ---------------------------------------------------- cos(a) 0 1/2 sqrt(2)/2 sqrt(3)/2 1 sin(a) 1 sqrt(3)/2 sqrt(2)/2 1/2 0 tan(a) 0 sqt(3)/3 1 sqrt(3) -- Examples ======== >>> from sympy.simplify.fu import TR4 >>> from sympy import pi >>> from sympy import cos, sin, tan, cot >>> for s in (0, pi/6, pi/4, pi/3, pi/2): ... print('%s %s %s %s' % (cos(s), sin(s), tan(s), cot(s))) ... 1 0 0 zoo sqrt(3)/2 1/2 sqrt(3)/3 sqrt(3) sqrt(2)/2 sqrt(2)/2 1 1 1/2 sqrt(3)/2 sqrt(3) sqrt(3)/3 0 1 zoo 0 """ # special values at 0, pi/6, pi/4, pi/3, pi/2 already handled return rv def _TR56(rv, f, g, h, max, pow): """Helper for TR5 and TR6 to replace f**2 with h(g**2) Options ======= max : controls size of exponent that can appear on f e.g. if max=4 then f**4 will be changed to h(g**2)**2. pow : controls whether the exponent must be a perfect power of 2 e.g. if pow=True (and max >= 6) then f**6 will not be changed but f**8 will be changed to h(g**2)**4 >>> from sympy.simplify.fu import _TR56 as T >>> from sympy.abc import x >>> from sympy import sin, cos >>> h = lambda x: 1 - x >>> T(sin(x)**3, sin, cos, h, 4, False) sin(x)**3 >>> T(sin(x)**6, sin, cos, h, 6, False) (-cos(x)**2 + 1)**3 >>> T(sin(x)**6, sin, cos, h, 6, True) sin(x)**6 >>> T(sin(x)**8, sin, cos, h, 10, True) (-cos(x)**2 + 1)**4 """ def _f(rv): # I'm not sure if this transformation should target all even powers # or only those expressible as powers of 2. Also, should it only # make the changes in powers that appear in sums -- making an isolated # change is not going to allow a simplification as far as I can tell. if not (rv.is_Pow and rv.base.func == f): return rv if (rv.exp < 0) == True: return rv if (rv.exp > max) == True: return rv if rv.exp == 2: return h(g(rv.base.args[0])**2) else: if rv.exp == 4: e = 2 elif not pow: if rv.exp % 2: return rv e = rv.exp//2 else: p = perfect_power(rv.exp) if not p: return rv e = rv.exp//2 return h(g(rv.base.args[0])**2)**e return bottom_up(rv, _f) def TR5(rv, max=4, pow=False): """Replacement of sin**2 with 1 - cos(x)**2. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR5 >>> from sympy.abc import x >>> from sympy import sin >>> TR5(sin(x)**2) -cos(x)**2 + 1 >>> TR5(sin(x)**-2) # unchanged sin(x)**(-2) >>> TR5(sin(x)**4) (-cos(x)**2 + 1)**2 """ return _TR56(rv, sin, cos, lambda x: 1 - x, max=max, pow=pow) def TR6(rv, max=4, pow=False): """Replacement of cos**2 with 1 - sin(x)**2. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR6 >>> from sympy.abc import x >>> from sympy import cos >>> TR6(cos(x)**2) -sin(x)**2 + 1 >>> TR6(cos(x)**-2) #unchanged cos(x)**(-2) >>> TR6(cos(x)**4) (-sin(x)**2 + 1)**2 """ return _TR56(rv, cos, sin, lambda x: 1 - x, max=max, pow=pow) def TR7(rv): """Lowering the degree of cos(x)**2 Examples ======== >>> from sympy.simplify.fu import TR7 >>> from sympy.abc import x >>> from sympy import cos >>> TR7(cos(x)**2) cos(2*x)/2 + 1/2 >>> TR7(cos(x)**2 + 1) cos(2*x)/2 + 3/2 """ def f(rv): if not (rv.is_Pow and rv.base.func == cos and rv.exp == 2): return rv return (1 + cos(2*rv.base.args[0]))/2 return bottom_up(rv, f) def TR8(rv, first=True): """Converting products of ``cos`` and/or ``sin`` to a sum or difference of ``cos`` and or ``sin`` terms. Examples ======== >>> from sympy.simplify.fu import TR8, TR7 >>> from sympy import cos, sin >>> TR8(cos(2)*cos(3)) cos(5)/2 + cos(1)/2 >>> TR8(cos(2)*sin(3)) sin(5)/2 + sin(1)/2 >>> TR8(sin(2)*sin(3)) -cos(5)/2 + cos(1)/2 """ def f(rv): if not ( rv.is_Mul or rv.is_Pow and rv.base.func in (cos, sin) and (rv.exp.is_integer or rv.base.is_positive)): return rv if first: n, d = [expand_mul(i) for i in rv.as_numer_denom()] newn = TR8(n, first=False) newd = TR8(d, first=False) if newn != n or newd != d: rv = gcd_terms(newn/newd) if rv.is_Mul and rv.args[0].is_Rational and \ len(rv.args) == 2 and rv.args[1].is_Add: rv = Mul(*rv.as_coeff_Mul()) return rv args = {cos: [], sin: [], None: []} for a in ordered(Mul.make_args(rv)): if a.func in (cos, sin): args[a.func].append(a.args[0]) elif (a.is_Pow and a.exp.is_Integer and a.exp > 0 and \ a.base.func in (cos, sin)): # XXX this is ok but pathological expression could be handled # more efficiently as in TRmorrie args[a.base.func].extend([a.base.args[0]]*a.exp) else: args[None].append(a) c = args[cos] s = args[sin] if not (c and s or len(c) > 1 or len(s) > 1): return rv args = args[None] n = min(len(c), len(s)) for i in range(n): a1 = s.pop() a2 = c.pop() args.append((sin(a1 + a2) + sin(a1 - a2))/2) while len(c) > 1: a1 = c.pop() a2 = c.pop() args.append((cos(a1 + a2) + cos(a1 - a2))/2) if c: args.append(cos(c.pop())) while len(s) > 1: a1 = s.pop() a2 = s.pop() args.append((-cos(a1 + a2) + cos(a1 - a2))/2) if s: args.append(sin(s.pop())) return TR8(expand_mul(Mul(*args))) return bottom_up(rv, f) def TR9(rv): """Sum of ``cos`` or ``sin`` terms as a product of ``cos`` or ``sin``. Examples ======== >>> from sympy.simplify.fu import TR9 >>> from sympy import cos, sin >>> TR9(cos(1) + cos(2)) 2*cos(1/2)*cos(3/2) >>> TR9(cos(1) + 2*sin(1) + 2*sin(2)) cos(1) + 4*sin(3/2)*cos(1/2) If no change is made by TR9, no re-arrangement of the expression will be made. For example, though factoring of common term is attempted, if the factored expression wasn't changed, the original expression will be returned: >>> TR9(cos(3) + cos(3)*cos(2)) cos(3) + cos(2)*cos(3) """ def f(rv): if not rv.is_Add: return rv def do(rv, first=True): # cos(a)+/-cos(b) can be combined into a product of cosines and # sin(a)+/-sin(b) can be combined into a product of cosine and # sine. # # If there are more than two args, the pairs which "work" will # have a gcd extractable and the remaining two terms will have # the above structure -- all pairs must be checked to find the # ones that work. args that don't have a common set of symbols # are skipped since this doesn't lead to a simpler formula and # also has the arbitrariness of combining, for example, the x # and y term instead of the y and z term in something like # cos(x) + cos(y) + cos(z). if not rv.is_Add: return rv args = list(ordered(rv.args)) if len(args) != 2: hit = False for i in range(len(args)): ai = args[i] if ai is None: continue for j in range(i + 1, len(args)): aj = args[j] if aj is None: continue was = ai + aj new = do(was) if new != was: args[i] = new # update in place args[j] = None hit = True break # go to next i if hit: rv = Add(*[_f for _f in args if _f]) if rv.is_Add: rv = do(rv) return rv # two-arg Add split = trig_split(*args) if not split: return rv gcd, n1, n2, a, b, iscos = split # application of rule if possible if iscos: if n1 == n2: return gcd*n1*2*cos((a + b)/2)*cos((a - b)/2) if n1 < 0: a, b = b, a return -2*gcd*sin((a + b)/2)*sin((a - b)/2) else: if n1 == n2: return gcd*n1*2*sin((a + b)/2)*cos((a - b)/2) if n1 < 0: a, b = b, a return 2*gcd*cos((a + b)/2)*sin((a - b)/2) return process_common_addends(rv, do) # DON'T sift by free symbols return bottom_up(rv, f) def TR10(rv, first=True): """Separate sums in ``cos`` and ``sin``. Examples ======== >>> from sympy.simplify.fu import TR10 >>> from sympy.abc import a, b, c >>> from sympy import cos, sin >>> TR10(cos(a + b)) -sin(a)*sin(b) + cos(a)*cos(b) >>> TR10(sin(a + b)) sin(a)*cos(b) + sin(b)*cos(a) >>> TR10(sin(a + b + c)) (-sin(a)*sin(b) + cos(a)*cos(b))*sin(c) + \ (sin(a)*cos(b) + sin(b)*cos(a))*cos(c) """ def f(rv): if not rv.func in (cos, sin): return rv f = rv.func arg = rv.args[0] if arg.is_Add: if first: args = list(ordered(arg.args)) else: args = list(arg.args) a = args.pop() b = Add._from_args(args) if b.is_Add: if f == sin: return sin(a)*TR10(cos(b), first=False) + \ cos(a)*TR10(sin(b), first=False) else: return cos(a)*TR10(cos(b), first=False) - \ sin(a)*TR10(sin(b), first=False) else: if f == sin: return sin(a)*cos(b) + cos(a)*sin(b) else: return cos(a)*cos(b) - sin(a)*sin(b) return rv return bottom_up(rv, f) def TR10i(rv): """Sum of products to function of sum. Examples ======== >>> from sympy.simplify.fu import TR10i >>> from sympy import cos, sin, pi, Add, Mul, sqrt, Symbol >>> from sympy.abc import x, y >>> TR10i(cos(1)*cos(3) + sin(1)*sin(3)) cos(2) >>> TR10i(cos(1)*sin(3) + sin(1)*cos(3) + cos(3)) cos(3) + sin(4) >>> TR10i(sqrt(2)*cos(x)*x + sqrt(6)*sin(x)*x) 2*sqrt(2)*x*sin(x + pi/6) """ global _ROOT2, _ROOT3, _invROOT3 if _ROOT2 is None: _roots() def f(rv): if not rv.is_Add: return rv def do(rv, first=True): # args which can be expressed as A*(cos(a)*cos(b)+/-sin(a)*sin(b)) # or B*(cos(a)*sin(b)+/-cos(b)*sin(a)) can be combined into # A*f(a+/-b) where f is either sin or cos. # # If there are more than two args, the pairs which "work" will have # a gcd extractable and the remaining two terms will have the above # structure -- all pairs must be checked to find the ones that # work. if not rv.is_Add: return rv args = list(ordered(rv.args)) if len(args) != 2: hit = False for i in range(len(args)): ai = args[i] if ai is None: continue for j in range(i + 1, len(args)): aj = args[j] if aj is None: continue was = ai + aj new = do(was) if new != was: args[i] = new # update in place args[j] = None hit = True break # go to next i if hit: rv = Add(*[_f for _f in args if _f]) if rv.is_Add: rv = do(rv) return rv # two-arg Add split = trig_split(*args, two=True) if not split: return rv gcd, n1, n2, a, b, same = split # identify and get c1 to be cos then apply rule if possible if same: # coscos, sinsin gcd = n1*gcd if n1 == n2: return gcd*cos(a - b) return gcd*cos(a + b) else: #cossin, cossin gcd = n1*gcd if n1 == n2: return gcd*sin(a + b) return gcd*sin(b - a) rv = process_common_addends( rv, do, lambda x: tuple(ordered(x.free_symbols))) # need to check for inducible pairs in ratio of sqrt(3):1 that # appeared in different lists when sorting by coefficient while rv.is_Add: byrad = defaultdict(list) for a in rv.args: hit = 0 if a.is_Mul: for ai in a.args: if ai.is_Pow and ai.exp is S.Half and \ ai.base.is_Integer: byrad[ai].append(a) hit = 1 break if not hit: byrad[S.One].append(a) # no need to check all pairs -- just check for the onees # that have the right ratio args = [] for a in byrad: for b in [_ROOT3*a, _invROOT3]: if b in byrad: for i in range(len(byrad[a])): if byrad[a][i] is None: continue for j in range(len(byrad[b])): if byrad[b][j] is None: continue was = Add(byrad[a][i] + byrad[b][j]) new = do(was) if new != was: args.append(new) byrad[a][i] = None byrad[b][j] = None break if args: rv = Add(*(args + [Add(*[_f for _f in v if _f]) for v in byrad.values()])) else: rv = do(rv) # final pass to resolve any new inducible pairs break return rv return bottom_up(rv, f) def TR11(rv, base=None): """Function of double angle to product. The ``base`` argument can be used to indicate what is the un-doubled argument, e.g. if 3*pi/7 is the base then cosine and sine functions with argument 6*pi/7 will be replaced. Examples ======== >>> from sympy.simplify.fu import TR11 >>> from sympy import cos, sin, pi >>> from sympy.abc import x >>> TR11(sin(2*x)) 2*sin(x)*cos(x) >>> TR11(cos(2*x)) -sin(x)**2 + cos(x)**2 >>> TR11(sin(4*x)) 4*(-sin(x)**2 + cos(x)**2)*sin(x)*cos(x) >>> TR11(sin(4*x/3)) 4*(-sin(x/3)**2 + cos(x/3)**2)*sin(x/3)*cos(x/3) If the arguments are simply integers, no change is made unless a base is provided: >>> TR11(cos(2)) cos(2) >>> TR11(cos(4), 2) -sin(2)**2 + cos(2)**2 There is a subtle issue here in that autosimplification will convert some higher angles to lower angles >>> cos(6*pi/7) + cos(3*pi/7) -cos(pi/7) + cos(3*pi/7) The 6*pi/7 angle is now pi/7 but can be targeted with TR11 by supplying the 3*pi/7 base: >>> TR11(_, 3*pi/7) -sin(3*pi/7)**2 + cos(3*pi/7)**2 + cos(3*pi/7) """ def f(rv): if not rv.func in (cos, sin): return rv if base: f = rv.func t = f(base*2) co = S.One if t.is_Mul: co, t = t.as_coeff_Mul() if not t.func in (cos, sin): return rv if rv.args[0] == t.args[0]: c = cos(base) s = sin(base) if f is cos: return (c**2 - s**2)/co else: return 2*c*s/co return rv elif not rv.args[0].is_Number: # make a change if the leading coefficient's numerator is # divisible by 2 c, m = rv.args[0].as_coeff_Mul(rational=True) if c.p % 2 == 0: arg = c.p//2*m/c.q c = TR11(cos(arg)) s = TR11(sin(arg)) if rv.func == sin: rv = 2*s*c else: rv = c**2 - s**2 return rv return bottom_up(rv, f) def TR12(rv, first=True): """Separate sums in ``tan``. Examples ======== >>> from sympy.simplify.fu import TR12 >>> from sympy.abc import x, y >>> from sympy import tan >>> from sympy.simplify.fu import TR12 >>> TR12(tan(x + y)) (tan(x) + tan(y))/(-tan(x)*tan(y) + 1) """ def f(rv): if not rv.func == tan: return rv arg = rv.args[0] if arg.is_Add: if first: args = list(ordered(arg.args)) else: args = list(arg.args) a = args.pop() b = Add._from_args(args) if b.is_Add: tb = TR12(tan(b), first=False) else: tb = tan(b) return (tan(a) + tb)/(1 - tan(a)*tb) return rv return bottom_up(rv, f) def TR12i(rv): """Combine tan arguments as (tan(y) + tan(x))/(tan(x)*tan(y) - 1) -> -tan(x + y) Examples ======== >>> from sympy.simplify.fu import TR12i >>> from sympy import tan >>> from sympy.abc import a, b, c >>> ta, tb, tc = [tan(i) for i in (a, b, c)] >>> TR12i((ta + tb)/(-ta*tb + 1)) tan(a + b) >>> TR12i((ta + tb)/(ta*tb - 1)) -tan(a + b) >>> TR12i((-ta - tb)/(ta*tb - 1)) tan(a + b) >>> eq = (ta + tb)/(-ta*tb + 1)**2*(-3*ta - 3*tc)/(2*(ta*tc - 1)) >>> TR12i(eq.expand()) -3*tan(a + b)*tan(a + c)/(2*(tan(a) + tan(b) - 1)) """ from sympy import factor def f(rv): if not (rv.is_Add or rv.is_Mul or rv.is_Pow): return rv n, d = rv.as_numer_denom() if not d.args or not n.args: return rv dok = {} def ok(di): m = as_f_sign_1(di) if m: g, f, s = m if s is S.NegativeOne and f.is_Mul and len(f.args) == 2 and \ all(isinstance(fi, tan) for fi in f.args): return g, f d_args = list(Mul.make_args(d)) for i, di in enumerate(d_args): m = ok(di) if m: g, t = m s = Add(*[_.args[0] for _ in t.args]) dok[s] = S.One d_args[i] = g continue if di.is_Add: di = factor(di) if di.is_Mul: d_args.extend(di.args) d_args[i] = S.One elif di.is_Pow and (di.exp.is_integer or di.base.is_positive): m = ok(di.base) if m: g, t = m s = Add(*[_.args[0] for _ in t.args]) dok[s] = di.exp d_args[i] = g**di.exp else: di = factor(di) if di.is_Mul: d_args.extend(di.args) d_args[i] = S.One if not dok: return rv def ok(ni): if ni.is_Add and len(ni.args) == 2: a, b = ni.args if isinstance(a, tan) and isinstance(b, tan): return a, b n_args = list(Mul.make_args(factor_terms(n))) hit = False for i, ni in enumerate(n_args): m = ok(ni) if not m: m = ok(-ni) if m: n_args[i] = S.NegativeOne else: if ni.is_Add: ni = factor(ni) if ni.is_Mul: n_args.extend(ni.args) n_args[i] = S.One continue elif ni.is_Pow and ( ni.exp.is_integer or ni.base.is_positive): m = ok(ni.base) if m: n_args[i] = S.One else: ni = factor(ni) if ni.is_Mul: n_args.extend(ni.args) n_args[i] = S.One continue else: continue else: n_args[i] = S.One hit = True s = Add(*[_.args[0] for _ in m]) ed = dok[s] newed = ed.extract_additively(S.One) if newed is not None: if newed: dok[s] = newed else: dok.pop(s) n_args[i] *= -tan(s) if hit: rv = Mul(*n_args)/Mul(*d_args)/Mul(*[(Add(*[ tan(a) for a in i.args]) - 1)**e for i, e in dok.items()]) return rv return bottom_up(rv, f) def TR13(rv): """Change products of ``tan`` or ``cot``. Examples ======== >>> from sympy.simplify.fu import TR13 >>> from sympy import tan, cot, cos >>> TR13(tan(3)*tan(2)) -tan(2)/tan(5) - tan(3)/tan(5) + 1 >>> TR13(cot(3)*cot(2)) cot(2)*cot(5) + 1 + cot(3)*cot(5) """ def f(rv): if not rv.is_Mul: return rv # XXX handle products of powers? or let power-reducing handle it? args = {tan: [], cot: [], None: []} for a in ordered(Mul.make_args(rv)): if a.func in (tan, cot): args[a.func].append(a.args[0]) else: args[None].append(a) t = args[tan] c = args[cot] if len(t) < 2 and len(c) < 2: return rv args = args[None] while len(t) > 1: t1 = t.pop() t2 = t.pop() args.append(1 - (tan(t1)/tan(t1 + t2) + tan(t2)/tan(t1 + t2))) if t: args.append(tan(t.pop())) while len(c) > 1: t1 = c.pop() t2 = c.pop() args.append(1 + cot(t1)*cot(t1 + t2) + cot(t2)*cot(t1 + t2)) if c: args.append(cot(c.pop())) return Mul(*args) return bottom_up(rv, f) def TRmorrie(rv): """Returns cos(x)*cos(2*x)*...*cos(2**(k-1)*x) -> sin(2**k*x)/(2**k*sin(x)) Examples ======== >>> from sympy.simplify.fu import TRmorrie, TR8, TR3 >>> from sympy.abc import x >>> from sympy import Mul, cos, pi >>> TRmorrie(cos(x)*cos(2*x)) sin(4*x)/(4*sin(x)) >>> TRmorrie(7*Mul(*[cos(x) for x in range(10)])) 7*sin(12)*sin(16)*cos(5)*cos(7)*cos(9)/(64*sin(1)*sin(3)) Sometimes autosimplification will cause a power to be not recognized. e.g. in the following, cos(4*pi/7) automatically simplifies to -cos(3*pi/7) so only 2 of the 3 terms are recognized: >>> TRmorrie(cos(pi/7)*cos(2*pi/7)*cos(4*pi/7)) -sin(3*pi/7)*cos(3*pi/7)/(4*sin(pi/7)) A touch by TR8 resolves the expression to a Rational >>> TR8(_) -1/8 In this case, if eq is unsimplified, the answer is obtained directly: >>> eq = cos(pi/9)*cos(2*pi/9)*cos(3*pi/9)*cos(4*pi/9) >>> TRmorrie(eq) 1/16 But if angles are made canonical with TR3 then the answer is not simplified without further work: >>> TR3(eq) sin(pi/18)*cos(pi/9)*cos(2*pi/9)/2 >>> TRmorrie(_) sin(pi/18)*sin(4*pi/9)/(8*sin(pi/9)) >>> TR8(_) cos(7*pi/18)/(16*sin(pi/9)) >>> TR3(_) 1/16 The original expression would have resolve to 1/16 directly with TR8, however: >>> TR8(eq) 1/16 References ========== http://en.wikipedia.org/wiki/Morrie%27s_law """ def f(rv): if not rv.is_Mul: return rv args = defaultdict(list) coss = {} other = [] for c in rv.args: b, e = c.as_base_exp() if e.is_Integer and isinstance(b, cos): co, a = b.args[0].as_coeff_Mul() args[a].append(co) coss[b] = e else: other.append(c) new = [] for a in args: c = args[a] c.sort() no = [] while c: k = 0 cc = ci = c[0] while cc in c: k += 1 cc *= 2 if k > 1: newarg = sin(2**k*ci*a)/2**k/sin(ci*a) # see how many times this can be taken take = None ccs = [] for i in range(k): cc /= 2 key = cos(a*cc, evaluate=False) ccs.append(cc) take = min(coss[key], take or coss[key]) # update exponent counts for i in range(k): cc = ccs.pop() key = cos(a*cc, evaluate=False) coss[key] -= take if not coss[key]: c.remove(cc) new.append(newarg**take) else: no.append(c.pop(0)) c[:] = no if new: rv = Mul(*(new + other + [ cos(k*a, evaluate=False) for a in args for k in args[a]])) return rv return bottom_up(rv, f) def TR14(rv, first=True): """Convert factored powers of sin and cos identities into simpler expressions. Examples ======== >>> from sympy.simplify.fu import TR14 >>> from sympy.abc import x, y >>> from sympy import cos, sin >>> TR14((cos(x) - 1)*(cos(x) + 1)) -sin(x)**2 >>> TR14((sin(x) - 1)*(sin(x) + 1)) -cos(x)**2 >>> p1 = (cos(x) + 1)*(cos(x) - 1) >>> p2 = (cos(y) - 1)*2*(cos(y) + 1) >>> p3 = (3*(cos(y) - 1))*(3*(cos(y) + 1)) >>> TR14(p1*p2*p3*(x - 1)) -18*(x - 1)*sin(x)**2*sin(y)**4 """ def f(rv): if not rv.is_Mul: return rv if first: # sort them by location in numerator and denominator # so the code below can just deal with positive exponents n, d = rv.as_numer_denom() if d is not S.One: newn = TR14(n, first=False) newd = TR14(d, first=False) if newn != n or newd != d: rv = newn/newd return rv other = [] process = [] for a in rv.args: if a.is_Pow: b, e = a.as_base_exp() if not (e.is_integer or b.is_positive): other.append(a) continue a = b else: e = S.One m = as_f_sign_1(a) if not m or m[1].func not in (cos, sin): if e is S.One: other.append(a) else: other.append(a**e) continue g, f, si = m process.append((g, e.is_Number, e, f, si, a)) # sort them to get like terms next to each other process = list(ordered(process)) # keep track of whether there was any change nother = len(other) # access keys keys = (g, t, e, f, si, a) = list(range(6)) while process: A = process.pop(0) if process: B = process[0] if A[e].is_Number and B[e].is_Number: # both exponents are numbers if A[f] == B[f]: if A[si] != B[si]: B = process.pop(0) take = min(A[e], B[e]) # reinsert any remainder # the B will likely sort after A so check it first if B[e] != take: rem = [B[i] for i in keys] rem[e] -= take process.insert(0, rem) elif A[e] != take: rem = [A[i] for i in keys] rem[e] -= take process.insert(0, rem) if isinstance(A[f], cos): t = sin else: t = cos other.append((-A[g]*B[g]*t(A[f].args[0])**2)**take) continue elif A[e] == B[e]: # both exponents are equal symbols if A[f] == B[f]: if A[si] != B[si]: B = process.pop(0) take = A[e] if isinstance(A[f], cos): t = sin else: t = cos other.append((-A[g]*B[g]*t(A[f].args[0])**2)**take) continue # either we are done or neither condition above applied other.append(A[a]**A[e]) if len(other) != nother: rv = Mul(*other) return rv return bottom_up(rv, f) def TR15(rv, max=4, pow=False): """Convert sin(x)*-2 to 1 + cot(x)**2. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR15 >>> from sympy.abc import x >>> from sympy import cos, sin >>> TR15(1 - 1/sin(x)**2) -cot(x)**2 """ def f(rv): if not (isinstance(rv, Pow) and isinstance(rv.base, sin)): return rv ia = 1/rv a = _TR56(ia, sin, cot, lambda x: 1 + x, max=max, pow=pow) if a != ia: rv = a return rv return bottom_up(rv, f) def TR16(rv, max=4, pow=False): """Convert cos(x)*-2 to 1 + tan(x)**2. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR16 >>> from sympy.abc import x >>> from sympy import cos, sin >>> TR16(1 - 1/cos(x)**2) -tan(x)**2 """ def f(rv): if not (isinstance(rv, Pow) and isinstance(rv.base, cos)): return rv ia = 1/rv a = _TR56(ia, cos, tan, lambda x: 1 + x, max=max, pow=pow) if a != ia: rv = a return rv return bottom_up(rv, f) def TR111(rv): """Convert f(x)**-i to g(x)**i where either ``i`` is an integer or the base is positive and f, g are: tan, cot; sin, csc; or cos, sec. Examples ======== >>> from sympy.simplify.fu import TR111 >>> from sympy.abc import x >>> from sympy import tan >>> TR111(1 - 1/tan(x)**2) -cot(x)**2 + 1 """ def f(rv): if not ( isinstance(rv, Pow) and (rv.base.is_positive or rv.exp.is_integer and rv.exp.is_negative)): return rv if isinstance(rv.base, tan): return cot(rv.base.args[0])**-rv.exp elif isinstance(rv.base, sin): return csc(rv.base.args[0])**-rv.exp elif isinstance(rv.base, cos): return sec(rv.base.args[0])**-rv.exp return rv return bottom_up(rv, f) def TR22(rv, max=4, pow=False): """Convert tan(x)**2 to sec(x)**2 - 1 and cot(x)**2 to csc(x)**2 - 1. See _TR56 docstring for advanced use of ``max`` and ``pow``. Examples ======== >>> from sympy.simplify.fu import TR22 >>> from sympy.abc import x >>> from sympy import tan, cot >>> TR22(1 + tan(x)**2) sec(x)**2 >>> TR22(1 + cot(x)**2) csc(x)**2 """ def f(rv): if not (isinstance(rv, Pow) and rv.base.func in (cot, tan)): return rv rv = _TR56(rv, tan, sec, lambda x: x - 1, max=max, pow=pow) rv = _TR56(rv, cot, csc, lambda x: x - 1, max=max, pow=pow) return rv return bottom_up(rv, f) def TRpower(rv): """Convert sin(x)**n and cos(x)**n with positive n to sums. Examples ======== >>> from sympy.simplify.fu import TRpower >>> from sympy.abc import x >>> from sympy import cos, sin >>> TRpower(sin(x)**6) -15*cos(2*x)/32 + 3*cos(4*x)/16 - cos(6*x)/32 + 5/16 >>> TRpower(sin(x)**3*cos(2*x)**4) (3*sin(x)/4 - sin(3*x)/4)*(cos(4*x)/2 + cos(8*x)/8 + 3/8) References ========== https://en.wikipedia.org/wiki/List_of_trigonometric_identities#Power-reduction_formulae """ def f(rv): if not (isinstance(rv, Pow) and isinstance(rv.base, (sin, cos))): return rv b, n = rv.as_base_exp() x = b.args[0] if n.is_Integer and n.is_positive: if n.is_odd and isinstance(b, cos): rv = 2**(1-n)*Add(*[binomial(n, k)*cos((n - 2*k)*x) for k in range((n + 1)/2)]) elif n.is_odd and isinstance(b, sin): rv = 2**(1-n)*(-1)**((n-1)/2)*Add(*[binomial(n, k)* (-1)**k*sin((n - 2*k)*x) for k in range((n + 1)/2)]) elif n.is_even and isinstance(b, cos): rv = 2**(1-n)*Add(*[binomial(n, k)*cos((n - 2*k)*x) for k in range(n/2)]) elif n.is_even and isinstance(b, sin): rv = 2**(1-n)*(-1)**(n/2)*Add(*[binomial(n, k)* (-1)**k*cos((n - 2*k)*x) for k in range(n/2)]) if n.is_even: rv += 2**(-n)*binomial(n, n/2) return rv return bottom_up(rv, f) def L(rv): """Return count of trigonometric functions in expression. Examples ======== >>> from sympy.simplify.fu import L >>> from sympy.abc import x >>> from sympy import cos, sin >>> L(cos(x)+sin(x)) 2 """ return S(rv.count(TrigonometricFunction)) # ============== end of basic Fu-like tools ===================== if SYMPY_DEBUG: (TR0, TR1, TR2, TR3, TR4, TR5, TR6, TR7, TR8, TR9, TR10, TR11, TR12, TR13, TR2i, TRmorrie, TR14, TR15, TR16, TR12i, TR111, TR22 )= list(map(debug, (TR0, TR1, TR2, TR3, TR4, TR5, TR6, TR7, TR8, TR9, TR10, TR11, TR12, TR13, TR2i, TRmorrie, TR14, TR15, TR16, TR12i, TR111, TR22))) # tuples are chains -- (f, g) -> lambda x: g(f(x)) # lists are choices -- [f, g] -> lambda x: min(f(x), g(x), key=objective) CTR1 = [(TR5, TR0), (TR6, TR0), identity] CTR2 = (TR11, [(TR5, TR0), (TR6, TR0), TR0]) CTR3 = [(TRmorrie, TR8, TR0), (TRmorrie, TR8, TR10i, TR0), identity] CTR4 = [(TR4, TR10i), identity] RL1 = (TR4, TR3, TR4, TR12, TR4, TR13, TR4, TR0) # XXX it's a little unclear how this one is to be implemented # see Fu paper of reference, page 7. What is the Union symbol referring to? # The diagram shows all these as one chain of transformations, but the # text refers to them being applied independently. Also, a break # if L starts to increase has not been implemented. RL2 = [ (TR4, TR3, TR10, TR4, TR3, TR11), (TR5, TR7, TR11, TR4), (CTR3, CTR1, TR9, CTR2, TR4, TR9, TR9, CTR4), identity, ] def fu(rv, measure=lambda x: (L(x), x.count_ops())): """Attempt to simplify expression by using transformation rules given in the algorithm by Fu et al. :func:`fu` will try to minimize the objective function ``measure``. By default this first minimizes the number of trig terms and then minimizes the number of total operations. Examples ======== >>> from sympy.simplify.fu import fu >>> from sympy import cos, sin, tan, pi, S, sqrt >>> from sympy.abc import x, y, a, b >>> fu(sin(50)**2 + cos(50)**2 + sin(pi/6)) 3/2 >>> fu(sqrt(6)*cos(x) + sqrt(2)*sin(x)) 2*sqrt(2)*sin(x + pi/3) CTR1 example >>> eq = sin(x)**4 - cos(y)**2 + sin(y)**2 + 2*cos(x)**2 >>> fu(eq) cos(x)**4 - 2*cos(y)**2 + 2 CTR2 example >>> fu(S.Half - cos(2*x)/2) sin(x)**2 CTR3 example >>> fu(sin(a)*(cos(b) - sin(b)) + cos(a)*(sin(b) + cos(b))) sqrt(2)*sin(a + b + pi/4) CTR4 example >>> fu(sqrt(3)*cos(x)/2 + sin(x)/2) sin(x + pi/3) Example 1 >>> fu(1-sin(2*x)**2/4-sin(y)**2-cos(x)**4) -cos(x)**2 + cos(y)**2 Example 2 >>> fu(cos(4*pi/9)) sin(pi/18) >>> fu(cos(pi/9)*cos(2*pi/9)*cos(3*pi/9)*cos(4*pi/9)) 1/16 Example 3 >>> fu(tan(7*pi/18)+tan(5*pi/18)-sqrt(3)*tan(5*pi/18)*tan(7*pi/18)) -sqrt(3) Objective function example >>> fu(sin(x)/cos(x)) # default objective function tan(x) >>> fu(sin(x)/cos(x), measure=lambda x: -x.count_ops()) # maximize op count sin(x)/cos(x) References ========== http://rfdz.ph-noe.ac.at/fileadmin/Mathematik_Uploads/ACDCA/ DESTIME2006/DES_contribs/Fu/simplification.pdf """ fRL1 = greedy(RL1, measure) fRL2 = greedy(RL2, measure) was = rv rv = sympify(rv) if not isinstance(rv, Expr): return rv.func(*[fu(a, measure=measure) for a in rv.args]) rv = TR1(rv) if rv.has(tan, cot): rv1 = fRL1(rv) if (measure(rv1) < measure(rv)): rv = rv1 if rv.has(tan, cot): rv = TR2(rv) if rv.has(sin, cos): rv1 = fRL2(rv) rv2 = TR8(TRmorrie(rv1)) rv = min([was, rv, rv1, rv2], key=measure) return min(TR2i(rv), rv, key=measure) def process_common_addends(rv, do, key2=None, key1=True): """Apply ``do`` to addends of ``rv`` that (if key1=True) share at least a common absolute value of their coefficient and the value of ``key2`` when applied to the argument. If ``key1`` is False ``key2`` must be supplied and will be the only key applied. """ # collect by absolute value of coefficient and key2 absc = defaultdict(list) if key1: for a in rv.args: c, a = a.as_coeff_Mul() if c < 0: c = -c a = -a # put the sign on `a` absc[(c, key2(a) if key2 else 1)].append(a) elif key2: for a in rv.args: absc[(S.One, key2(a))].append(a) else: raise ValueError('must have at least one key') args = [] hit = False for k in absc: v = absc[k] c, _ = k if len(v) > 1: e = Add(*v, evaluate=False) new = do(e) if new != e: e = new hit = True args.append(c*e) else: args.append(c*v[0]) if hit: rv = Add(*args) return rv fufuncs = ''' TR0 TR1 TR2 TR3 TR4 TR5 TR6 TR7 TR8 TR9 TR10 TR10i TR11 TR12 TR13 L TR2i TRmorrie TR12i TR14 TR15 TR16 TR111 TR22'''.split() FU = dict(list(zip(fufuncs, list(map(locals().get, fufuncs))))) def _roots(): global _ROOT2, _ROOT3, _invROOT3 _ROOT2, _ROOT3 = sqrt(2), sqrt(3) _invROOT3 = 1/_ROOT3 _ROOT2 = None def trig_split(a, b, two=False): """Return the gcd, s1, s2, a1, a2, bool where If two is False (default) then:: a + b = gcd*(s1*f(a1) + s2*f(a2)) where f = cos if bool else sin else: if bool, a + b was +/- cos(a1)*cos(a2) +/- sin(a1)*sin(a2) and equals n1*gcd*cos(a - b) if n1 == n2 else n1*gcd*cos(a + b) else a + b was +/- cos(a1)*sin(a2) +/- sin(a1)*cos(a2) and equals n1*gcd*sin(a + b) if n1 = n2 else n1*gcd*sin(b - a) Examples ======== >>> from sympy.simplify.fu import trig_split >>> from sympy.abc import x, y, z >>> from sympy import cos, sin, sqrt >>> trig_split(cos(x), cos(y)) (1, 1, 1, x, y, True) >>> trig_split(2*cos(x), -2*cos(y)) (2, 1, -1, x, y, True) >>> trig_split(cos(x)*sin(y), cos(y)*sin(y)) (sin(y), 1, 1, x, y, True) >>> trig_split(cos(x), -sqrt(3)*sin(x), two=True) (2, 1, -1, x, pi/6, False) >>> trig_split(cos(x), sin(x), two=True) (sqrt(2), 1, 1, x, pi/4, False) >>> trig_split(cos(x), -sin(x), two=True) (sqrt(2), 1, -1, x, pi/4, False) >>> trig_split(sqrt(2)*cos(x), -sqrt(6)*sin(x), two=True) (2*sqrt(2), 1, -1, x, pi/6, False) >>> trig_split(-sqrt(6)*cos(x), -sqrt(2)*sin(x), two=True) (-2*sqrt(2), 1, 1, x, pi/3, False) >>> trig_split(cos(x)/sqrt(6), sin(x)/sqrt(2), two=True) (sqrt(6)/3, 1, 1, x, pi/6, False) >>> trig_split(-sqrt(6)*cos(x)*sin(y), -sqrt(2)*sin(x)*sin(y), two=True) (-2*sqrt(2)*sin(y), 1, 1, x, pi/3, False) >>> trig_split(cos(x), sin(x)) >>> trig_split(cos(x), sin(z)) >>> trig_split(2*cos(x), -sin(x)) >>> trig_split(cos(x), -sqrt(3)*sin(x)) >>> trig_split(cos(x)*cos(y), sin(x)*sin(z)) >>> trig_split(cos(x)*cos(y), sin(x)*sin(y)) >>> trig_split(-sqrt(6)*cos(x), sqrt(2)*sin(x)*sin(y), two=True) """ global _ROOT2, _ROOT3, _invROOT3 if _ROOT2 is None: _roots() a, b = [Factors(i) for i in (a, b)] ua, ub = a.normal(b) gcd = a.gcd(b).as_expr() n1 = n2 = 1 if S.NegativeOne in ua.factors: ua = ua.quo(S.NegativeOne) n1 = -n1 elif S.NegativeOne in ub.factors: ub = ub.quo(S.NegativeOne) n2 = -n2 a, b = [i.as_expr() for i in (ua, ub)] def pow_cos_sin(a, two): """Return ``a`` as a tuple (r, c, s) such that ``a = (r or 1)*(c or 1)*(s or 1)``. Three arguments are returned (radical, c-factor, s-factor) as long as the conditions set by ``two`` are met; otherwise None is returned. If ``two`` is True there will be one or two non-None values in the tuple: c and s or c and r or s and r or s or c with c being a cosine function (if possible) else a sine, and s being a sine function (if possible) else oosine. If ``two`` is False then there will only be a c or s term in the tuple. ``two`` also require that either two cos and/or sin be present (with the condition that if the functions are the same the arguments are different or vice versa) or that a single cosine or a single sine be present with an optional radical. If the above conditions dictated by ``two`` are not met then None is returned. """ c = s = None co = S.One if a.is_Mul: co, a = a.as_coeff_Mul() if len(a.args) > 2 or not two: return None if a.is_Mul: args = list(a.args) else: args = [a] a = args.pop(0) if isinstance(a, cos): c = a elif isinstance(a, sin): s = a elif a.is_Pow and a.exp is S.Half: # autoeval doesn't allow -1/2 co *= a else: return None if args: b = args[0] if isinstance(b, cos): if c: s = b else: c = b elif isinstance(b, sin): if s: c = b else: s = b elif b.is_Pow and b.exp is S.Half: co *= b else: return None return co if co is not S.One else None, c, s elif isinstance(a, cos): c = a elif isinstance(a, sin): s = a if c is None and s is None: return co = co if co is not S.One else None return co, c, s # get the parts m = pow_cos_sin(a, two) if m is None: return coa, ca, sa = m m = pow_cos_sin(b, two) if m is None: return cob, cb, sb = m # check them if (not ca) and cb or ca and isinstance(ca, sin): coa, ca, sa, cob, cb, sb = cob, cb, sb, coa, ca, sa n1, n2 = n2, n1 if not two: # need cos(x) and cos(y) or sin(x) and sin(y) c = ca or sa s = cb or sb if not isinstance(c, s.func): return None return gcd, n1, n2, c.args[0], s.args[0], isinstance(c, cos) else: if not coa and not cob: if (ca and cb and sa and sb): if isinstance(ca, sa.func) is not isinstance(cb, sb.func): return args = {j.args for j in (ca, sa)} if not all(i.args in args for i in (cb, sb)): return return gcd, n1, n2, ca.args[0], sa.args[0], isinstance(ca, sa.func) if ca and sa or cb and sb or \ two and (ca is None and sa is None or cb is None and sb is None): return c = ca or sa s = cb or sb if c.args != s.args: return if not coa: coa = S.One if not cob: cob = S.One if coa is cob: gcd *= _ROOT2 return gcd, n1, n2, c.args[0], pi/4, False elif coa/cob == _ROOT3: gcd *= 2*cob return gcd, n1, n2, c.args[0], pi/3, False elif coa/cob == _invROOT3: gcd *= 2*coa return gcd, n1, n2, c.args[0], pi/6, False def as_f_sign_1(e): """If ``e`` is a sum that can be written as ``g*(a + s)`` where ``s`` is ``+/-1``, return ``g``, ``a``, and ``s`` where ``a`` does not have a leading negative coefficient. Examples ======== >>> from sympy.simplify.fu import as_f_sign_1 >>> from sympy.abc import x >>> as_f_sign_1(x + 1) (1, x, 1) >>> as_f_sign_1(x - 1) (1, x, -1) >>> as_f_sign_1(-x + 1) (-1, x, -1) >>> as_f_sign_1(-x - 1) (-1, x, 1) >>> as_f_sign_1(2*x + 2) (2, x, 1) """ if not e.is_Add or len(e.args) != 2: return # exact match a, b = e.args if a in (S.NegativeOne, S.One): g = S.One if b.is_Mul and b.args[0].is_Number and b.args[0] < 0: a, b = -a, -b g = -g return g, b, a # gcd match a, b = [Factors(i) for i in e.args] ua, ub = a.normal(b) gcd = a.gcd(b).as_expr() if S.NegativeOne in ua.factors: ua = ua.quo(S.NegativeOne) n1 = -1 n2 = 1 elif S.NegativeOne in ub.factors: ub = ub.quo(S.NegativeOne) n1 = 1 n2 = -1 else: n1 = n2 = 1 a, b = [i.as_expr() for i in (ua, ub)] if a is S.One: a, b = b, a n1, n2 = n2, n1 if n1 == -1: gcd = -gcd n2 = -n2 if b is S.One: return gcd, a, n2 def _osborne(e, d): """Replace all hyperbolic functions with trig functions using the Osborne rule. Notes ===== ``d`` is a dummy variable to prevent automatic evaluation of trigonometric/hyperbolic functions. References ========== http://en.wikipedia.org/wiki/Hyperbolic_function """ def f(rv): if not isinstance(rv, HyperbolicFunction): return rv a = rv.args[0] a = a*d if not a.is_Add else Add._from_args([i*d for i in a.args]) if isinstance(rv, sinh): return I*sin(a) elif isinstance(rv, cosh): return cos(a) elif isinstance(rv, tanh): return I*tan(a) elif isinstance(rv, coth): return cot(a)/I elif isinstance(rv, sech): return sec(a) elif isinstance(rv, csch): return csc(a)/I else: raise NotImplementedError('unhandled %s' % rv.func) return bottom_up(e, f) def _osbornei(e, d): """Replace all trig functions with hyperbolic functions using the Osborne rule. Notes ===== ``d`` is a dummy variable to prevent automatic evaluation of trigonometric/hyperbolic functions. References ========== http://en.wikipedia.org/wiki/Hyperbolic_function """ def f(rv): if not isinstance(rv, TrigonometricFunction): return rv const, x = rv.args[0].as_independent(d, as_Add=True) a = x.xreplace({d: S.One}) + const*I if isinstance(rv, sin): return sinh(a)/I elif isinstance(rv, cos): return cosh(a) elif isinstance(rv, tan): return tanh(a)/I elif isinstance(rv, cot): return coth(a)*I elif isinstance(rv, sec): return sech(a) elif isinstance(rv, csc): return csch(a)*I else: raise NotImplementedError('unhandled %s' % rv.func) return bottom_up(e, f) def hyper_as_trig(rv): """Return an expression containing hyperbolic functions in terms of trigonometric functions. Any trigonometric functions initially present are replaced with Dummy symbols and the function to undo the masking and the conversion back to hyperbolics is also returned. It should always be true that:: t, f = hyper_as_trig(expr) expr == f(t) Examples ======== >>> from sympy.simplify.fu import hyper_as_trig, fu >>> from sympy.abc import x >>> from sympy import cosh, sinh >>> eq = sinh(x)**2 + cosh(x)**2 >>> t, f = hyper_as_trig(eq) >>> f(fu(t)) cosh(2*x) References ========== http://en.wikipedia.org/wiki/Hyperbolic_function """ from sympy.simplify.simplify import signsimp from sympy.simplify.radsimp import collect # mask off trig functions trigs = rv.atoms(TrigonometricFunction) reps = [(t, Dummy()) for t in trigs] masked = rv.xreplace(dict(reps)) # get inversion substitutions in place reps = [(v, k) for k, v in reps] d = Dummy() return _osborne(masked, d), lambda x: collect(signsimp( _osbornei(x, d).xreplace(dict(reps))), S.ImaginaryUnit) def sincos_to_sum(expr): """Convert products and powers of sin and cos to sums. Applied power reduction TRpower first, then expands products, and converts products to sums with TR8. Examples ======== >>> from sympy.simplify.fu import sincos_to_sum >>> from sympy.abc import x >>> from sympy import cos, sin >>> sincos_to_sum(16*sin(x)**3*cos(2*x)**2) 7*sin(x) - 5*sin(3*x) + 3*sin(5*x) - sin(7*x) """ if not expr.has(cos, sin): return expr else: return TR8(expand_mul(TRpower(expr)))