trig: write cos(pi/257) as a function of radicals
trig: write cos(pi/257) as a function of radicals

Implements cos(pi/257).rewrite(sqrt).  A test for checking
cos(pi/257).rewrite(sqrt) would take quite a long time.  Is it
worthwhile to put in a test?

drufat/sympy,emon10005/sympy,Gadal/sympy,Designist/sympy,kevalds51/sympy,VaibhavAgarwalVA/sympy,drufat/sympy,cswiercz/sympy,kaichogami/sympy,bukzor/sympy,oliverlee/sympy,aktech/sympy,sahmed95/sympy,Arafatk/sympy,jerli/sympy,wanglongqi/sympy,meghana1995/sympy,atreyv/sympy,cswiercz/sympy,grevutiu-gabriel/sympy,ChristinaZografou/sympy,rahuldan/sympy,wanglongqi/sympy,Mitchkoens/sympy,garvitr/sympy,yashsharan/sympy,AkademieOlympia/sympy,debugger22/sympy,AkademieOlympia/sympy,wyom/sympy,chaffra/sympy,vipulroxx/sympy,toolforger/sympy,postvakje/sympy,asm666/sympy,iamutkarshtiwari/sympy,asm666/sympy,moble/sympy,ga7g08/sympy,grevutiu-gabriel/sympy,ga7g08/sympy,emon10005/sympy,shikil/sympy,kevalds51/sympy,yashsharan/sympy,abloomston/sympy,aktech/sympy,kumarkrishna/sympy,liangjiaxing/sympy,jaimahajan1997/sympy,grevutiu-gabriel/sympy,Curious72/sympy,Shaswat27/sympy,Titan-C/sympy,farhaanbukhsh/sympy,souravsingh/sympy,mcdaniel67/sympy,iamutkarshtiwari/sympy,pbrady/sympy,chaffra/sympy,ahhda/sympy,skidzo/sympy,jerli/sympy,mafiya69/sympy,maniteja123/sympy,AkademieOlympia/sympy,Curious72/sympy,farhaanbukhsh/sympy,mafiya69/sympy,lindsayad/sympy,sahilshekhawat/sympy,pandeyadarsh/sympy,mafiya69/sympy,jbbskinny/sympy,garvitr/sympy,pandeyadarsh/sympy,shikil/sympy,VaibhavAgarwalVA/sympy,oliverlee/sympy,Vishluck/sympy,pbrady/sympy,kaichogami/sympy,VaibhavAgarwalVA/sympy,Arafatk/sympy,rahuldan/sympy,atsao72/sympy,Vishluck/sympy,pandeyadarsh/sympy,ahhda/sympy,lindsayad/sympy,postvakje/sympy,abloomston/sympy,atreyv/sympy,Designist/sympy,kevalds51/sympy,jbbskinny/sympy,kaushik94/sympy,abhiii5459/sympy,yukoba/sympy,Gadal/sympy,jerli/sympy,ChristinaZografou/sympy,rahuldan/sympy,wyom/sympy,Mitchkoens/sympy,farhaanbukhsh/sympy,saurabhjn76/sympy,kaushik94/sympy,vipulroxx/sympy,atsao72/sympy,ahhda/sympy,emon10005/sympy,oliverlee/sympy,liangjiaxing/sympy,saurabhjn76/sympy,ga7g08/sympy,maniteja123/sympy,skidzo/sympy,jaimahajan1997/sympy,yukoba/sympy,hargup/sympy,debugger22/sympy,kaichogami/sympy,Gadal/sympy,maniteja123/sympy,madan96/sympy,yukoba/sympy,jbbskinny/sympy,kumarkrishna/sympy,aktech/sympy,wyom/sympy,abhiii5459/sympy,hargup/sympy,moble/sympy,postvakje/sympy,sahmed95/sympy,abloomston/sympy,cswiercz/sympy,Curious72/sympy,Shaswat27/sympy,Mitchkoens/sympy,yashsharan/sympy,shikil/sympy,meghana1995/sympy,sampadsaha5/sympy,atreyv/sympy,jaimahajan1997/sympy,madan96/sympy,MechCoder/sympy,pbrady/sympy,Shaswat27/sympy,ChristinaZografou/sympy,mcdaniel67/sympy,sahilshekhawat/sympy,kaushik94/sympy,meghana1995/sympy,garvitr/sympy,iamutkarshtiwari/sympy,skidzo/sympy,Davidjohnwilson/sympy,sampadsaha5/sympy,kumarkrishna/sympy,MechCoder/sympy,wanglongqi/sympy,sahilshekhawat/sympy,saurabhjn76/sympy,hargup/sympy,Designist/sympy,drufat/sympy,souravsingh/sympy,moble/sympy,Davidjohnwilson/sympy,bukzor/sympy,Titan-C/sympy,Titan-C/sympy,chaffra/sympy,abhiii5459/sympy,atsao72/sympy,asm666/sympy,liangjiaxing/sympy,lindsayad/sympy,debugger22/sympy,sampadsaha5/sympy,toolforger/sympy,sahmed95/sympy,toolforger/sympy,mcdaniel67/sympy,bukzor/sympy,madan96/sympy,vipulroxx/sympy,Vishluck/sympy,Arafatk/sympy,MechCoder/sympy,Davidjohnwilson/sympy,souravsingh/sympy