розв`язати cos²x - sin²x=√2/2

Question

розв`язати

cos²x - sin²x=√2/2

Answer 1

cos^2 x - sin^2 x = cos 2x;

cos 2x = sqrt(2)/2

2x = +-pi/4 + 2pi*k, k in Integers;

x = +-pi/8 + pi*k, k in Integers.