Question

2cos^2(3π/2-x/4)-2=0

Answer 1

cos^2 x2 =1-sin^2 x2
sin^2 x2 -(1-sin^2 x2 )=sin^2 x2-1+sin^2 x2=2sin^2 x2-1=2(1-cosx)/2-1=1-cos x-1=-cos x