Question 610543
cos(2x) = cos^2(x) - sin^2(x)


1 - [cos^2(x) - sin^2(x)] = 2 sin^2(x)


1 - cos^2(x) + sin^2(x) = 2 sin^2(x)


1 - cos^2(x) = sin^2(x)


1 = sin^2(x) + cos^2(x)