doctest fix for: Re/Im(tanh) wrong formula

[rwst]

In analogy to #19791:

sage: tanh(1+2*I).n()
1.16673625724092 - 0.243458201185725*I
sage: tanh(1+2*I).real().n()
0.202053272732553
sage: tanh(1+2*I).imag().n()
-0.579697798322816
sage: tanh(x).real()
tanh(real_part(x))/(tan(imag_part(x))^2*tanh(real_part(x))^2 + 1)
sage: tanh(x).imag()
tan(imag_part(x))/(tan(imag_part(x))^2*tanh(real_part(x))^2 + 1)

See for example http://dlmf.nist.gov/4.35.E36

Will be fixed in Pynac-0.6.3 and should be doctested here.

CC: @behackl

Component: symbolics

Author: Ralf Stephan

Branch/Commit: 9eafdee

Reviewer: Marc Mezzarobba

Issue created by migration from https://trac.sagemath.org/ticket/20098

[rwst]

Description changed:

--- 
+++ 
@@ -12,4 +12,6 @@
 sage: tanh(x).imag()
 tan(imag_part(x))/(tan(imag_part(x))^2*tanh(real_part(x))^2 + 1)
 ```
+See for example http://dlmf.nist.gov/4.35.E36
+
 Will be fixed in Pynac-0.6.3 and should be doctested here.

[rwst]

Branch: u/rws/re_im_tanh__wrong_formula

[rwst]

New commits:

9eafdee

20098: doctest fix for Re/Im(tanh) wrong formula

[rwst]

Commit: 9eafdee

[rwst]

Author: Ralf Stephan

[mezzarobba]

Reviewer: Marc Mezzarobba

[vbraun]

Changed branch from u/rws/re_im_tanh__wrong_formula to 9eafdee