Cos2x+cos^2(x-pi/2)=0 75

Question

Cos2x+cos^2(x-pi/2)=0 75

Answer 1

Cos^2(x-90)=sin^x
Cos2x=cos^2x-sin^2x
cos^2x-sin^2x+sin^2x=3/4
cosx=+-sqrt(3)/2
X=+-p/6+2pk