added methods to find the period of trigonometric functions
added methods to find the period of trigonometric functions

yashsharan/sympy,souravsingh/sympy,madan96/sympy,postvakje/sympy,sampadsaha5/sympy,skidzo/sympy,madan96/sympy,skidzo/sympy,aktech/sympy,aktech/sympy,madan96/sympy,souravsingh/sympy,sampadsaha5/sympy,skidzo/sympy,souravsingh/sympy,drufat/sympy,drufat/sympy,chaffra/sympy,chaffra/sympy,jaimahajan1997/sympy,kaushik94/sympy,jaimahajan1997/sympy,drufat/sympy,postvakje/sympy,yashsharan/sympy,kaushik94/sympy,sampadsaha5/sympy,postvakje/sympy,yashsharan/sympy,kaushik94/sympy,aktech/sympy,jaimahajan1997/sympy,chaffra/sympy