My book is showing 1 - (sin^2)x = (cos^2)x, is this true? Yes, draw a right triangle and label one of the angles x. Now label each side a, b and c. Ok so what is sin (x) in terms of a,b,c? So what is sin 2 (x)? Continue this for cos 2 (x) and you'll see the result holds. If so under what subject do I find more information about this. Z2gpYu.

what is 1 cos 2x