Sin^2x - Cos^2x =√2/2

Question

Sin^2x - Cos^2x =√2/2

Answer 1

-cos(2x)=√2/2
cos2x=-√2/2
2x=+-arccos(-√2/2)+2pi*n,n∈Z
2x=+-3pi/4+2pi*n,n∈Z
x=+-3pi/8+pi*n,n∈Z