Improved docstrings and edited atanh and atan
Improved docstrings and edited atanh and atan

Improved docstrings of tan and tanh by explaining algo used.
Separated formula based evaluation of atan and atanh from main functions.

VaibhavAgarwalVA/sympy,Shaswat27/sympy,toolforger/sympy,VaibhavAgarwalVA/sympy,postvakje/sympy,Curious72/sympy,sahmed95/sympy,AkademieOlympia/sympy,ChristinaZografou/sympy,farhaanbukhsh/sympy,debugger22/sympy,wyom/sympy,hargup/sympy,souravsingh/sympy,moble/sympy,abhiii5459/sympy,Arafatk/sympy,jbbskinny/sympy,ahhda/sympy,yukoba/sympy,shikil/sympy,bukzor/sympy,VaibhavAgarwalVA/sympy,jaimahajan1997/sympy,garvitr/sympy,souravsingh/sympy,garvitr/sympy,Shaswat27/sympy,debugger22/sympy,atsao72/sympy,kaichogami/sympy,lindsayad/sympy,sampadsaha5/sympy,Titan-C/sympy,madan96/sympy,jbbskinny/sympy,Curious72/sympy,Titan-C/sympy,debugger22/sympy,yashsharan/sympy,abloomston/sympy,emon10005/sympy,jaimahajan1997/sympy,cswiercz/sympy,pandeyadarsh/sympy,chaffra/sympy,sahmed95/sympy,mcdaniel67/sympy,iamutkarshtiwari/sympy,Davidjohnwilson/sympy,emon10005/sympy,farhaanbukhsh/sympy,wyom/sympy,kevalds51/sympy,wyom/sympy,drufat/sympy,MechCoder/sympy,kevalds51/sympy,oliverlee/sympy,maniteja123/sympy,kaushik94/sympy,mafiya69/sympy,rahuldan/sympy,emon10005/sympy,mafiya69/sympy,kumarkrishna/sympy,drufat/sympy,Designist/sympy,atsao72/sympy,atsao72/sympy,cswiercz/sympy,lindsayad/sympy,mafiya69/sympy,kaushik94/sympy,sampadsaha5/sympy,abhiii5459/sympy,hargup/sympy,mcdaniel67/sympy,ga7g08/sympy,Davidjohnwilson/sympy,kaushik94/sympy,Vishluck/sympy,Vishluck/sympy,Titan-C/sympy,aktech/sympy,rahuldan/sympy,Gadal/sympy,bukzor/sympy,oliverlee/sympy,MechCoder/sympy,atreyv/sympy,skidzo/sympy,wanglongqi/sympy,kumarkrishna/sympy,lindsayad/sympy,ChristinaZografou/sympy,shikil/sympy,mcdaniel67/sympy,jbbskinny/sympy,toolforger/sympy,yashsharan/sympy,jaimahajan1997/sympy,saurabhjn76/sympy,kevalds51/sympy,asm666/sympy,sahmed95/sympy,atreyv/sympy,drufat/sympy,toolforger/sympy,jerli/sympy,MechCoder/sympy,kaichogami/sympy,Vishluck/sympy,skidzo/sympy,bukzor/sympy,shikil/sympy,grevutiu-gabriel/sympy,iamutkarshtiwari/sympy,kumarkrishna/sympy,jerli/sympy,sampadsaha5/sympy,souravsingh/sympy,atreyv/sympy,oliverlee/sympy,AkademieOlympia/sympy,grevutiu-gabriel/sympy,abloomston/sympy,moble/sympy,kaichogami/sympy,chaffra/sympy,pandeyadarsh/sympy,saurabhjn76/sympy,yukoba/sympy,Gadal/sympy,moble/sympy,pandeyadarsh/sympy,rahuldan/sympy,madan96/sympy,aktech/sympy,Designist/sympy,chaffra/sympy,ahhda/sympy,cswiercz/sympy,asm666/sympy,farhaanbukhsh/sympy,skidzo/sympy,iamutkarshtiwari/sympy,ga7g08/sympy,saurabhjn76/sympy,ahhda/sympy,hargup/sympy,abhiii5459/sympy,Designist/sympy,madan96/sympy,Curious72/sympy,postvakje/sympy,grevutiu-gabriel/sympy,aktech/sympy,asm666/sympy,wanglongqi/sympy,yukoba/sympy,Shaswat27/sympy,maniteja123/sympy,ChristinaZografou/sympy,garvitr/sympy,Arafatk/sympy,yashsharan/sympy,Davidjohnwilson/sympy,abloomston/sympy,Gadal/sympy,maniteja123/sympy,AkademieOlympia/sympy,wanglongqi/sympy,postvakje/sympy,Arafatk/sympy,ga7g08/sympy,jerli/sympy