Integral of sin^4(x) | Integration using trigonometric identities | Khan Academy
It is a bit involved, but we can use u-substitution to find the integral of sin^4(x) ... (In case anyone wanted) A quick derivation for the trig identity {sin^2x=1/2(1-cos2x)} : 1. Start with: sin^2x+cos^2x=1 and cos2a=cos^2x-sin^2x...