Merge a2d0ed7 into d3840c1

autodiff/admath/admath.py

@@ -20,7 +20,7 @@ def sin(x):
 def cos(x):
     """Calculate cosine of the input
 
-        Keyword arguments:
+        Keyword arguments:numpy.tan
         x -- a real number or a dual number
 
         Return:
@@ -33,6 +33,23 @@ def cos(x):
     else:
         return np.cos(x)
 
+def tan(x):
+    """Calculate tangent of the input
+
+        Keyword arguments:
+        x -- a real number or a dual number
+
+        Return:
+        the tanget value
+    """
+    if (isinstance(x,Dual)):
+        x.der = 1/np.cos(x.val)**2*x.der
+        x.val = np.tan(x.val)
+        return x
+    else:
+        return np.tan(x)
+
+
 def log(x):
     """Calculate the natural log of the input
 

test/test_admath.py

@@ -37,6 +37,13 @@ def test2__cos_fn__():
         assert np.cos(test) == f.val
         assert -1*np.sin(test) == f.der
 
+def test1__tan_fn__():
+    x = Dual(0)
+    f = admath.tan(x)
+    assert f.val == 0
+    assert f.der == 1
+    assert admath.tan(0) == 0
+
 
 def test_log_fn__():
     tests = np.linspace(1,100,15)