Jika 5 sin x = 2 cos x, dan x berada di kuadran 1, maka (sin x- cos x) ^2=.....

(sin x - cos x)^2 = sin^2 x + cos^2 x - 2cos x. sin x = 1 - 5 sin x. sin x = 1 - 5 sin^2 x

Jadi, (sin x - cos x)^2 = 1 - 5 sin^2 x