[sin^n(x)]'=nsin^(n-1)(x)cosx[cosnx]'=-nsinnxy'=[sin^n(x)]'cos nx +[cosnx]'sin^n(x)=nsin^(n-1)(x)cosxcos nx-nsinnxsin^n(x) =nsin^(n-1)(x)(coscosnx-sinnxsinx)=nsin^(n-1)(x)cos(n+1)x cos(a+b)=cosacosb-s...