[Merged by Bors] - feat(analysis/special_functions/complex/arg): arg_neg
lemmas
#11503
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Add lemmas about the value of
arg (-x)
: one each for positive andnegative sign of
x.im
, twoiff
lemmas saying exactly when it'sequal to
arg x - π
orarg x + π
, and a simpler lemma giving thevalue of
(arg (-x) : real.angle)
for any nonzerox
.These replace the previous lemmas
arg_eq_arg_neg_add_pi_of_im_nonneg_of_re_neg
andarg_eq_arg_neg_sub_pi_of_im_neg_of_re_neg
, which are strictly lessgeneral (they have a hypothesis
x.re < 0
that's not needed unlessthe imaginary part is 0). Those two lemmas are unused in current
mathlib (they were used in the proof of
cos_arg
before the golfingin #10365) and it seems reasonable to me to replace them with the more
general lemmas.