Question

Buktikan bahwa sinxsin2x+cosxcos2x=cosx

Answer 1

Verified answer

Sinx sin 2x + cos x cos 2x
=> cos x cos 2x + sin x cos 2x
=> cos (x -2x)
=> cos (-x)
=> cos x
cos (-x) = cos x karena cos(-x) ada pada kuadran IV.