sin(x+pi)=-sin(x)=sin(-x)=cos(pi/2)
cos (x+pi)=-cos(x)
So according to the question:
cos(pi/2 +x)=cos(x)
Using the solution of cos, obtain:
(pi/2) + x = 2pi +- (x)
case#1: (pi/2) + x = 2pi + (x)
But here, the value of x is canceled, just
case#2: (pi/2) + x = 2pi - (x)
answer------------>>>>>>>>> x=pi-pi/4