已知a的终边过点P【-根号3,y】且sina=根号3除以4乘以Y【Y不等于0】求cosa,tana的值

P(-√3,y)则r=√(x²+y²)=√(3+y²)所以sina=y/r=y/√(3+y²)=√3y/4r=√(3+y²)=4/√3y²=7/3y=±√21/3sina=±√7/4所以cosa=x/r=-√3/(4/√3)=-3/4tana=sina/cosa=√7/3或-√7/3...