(1) Evaluate cos5xdx\displaystyle \int{{\cos}^{{5}}{x}}{\left.{d}{x}\right.}

Hint: Express cos4x\displaystyle {{\cos}^{{4}}{x}} in terms of sinx\displaystyle {\sin{{x}}}. Then use the substitution u=sinx\displaystyle {u}={\sin{{x}}}. Back substitute to write your soluton in terms of x\displaystyle {x}

solution = + C
 

(2) Evaluate cos2xdx\displaystyle \int{{\cos}^{{2}}{x}}{\left.{d}{x}\right.}

Hint: Use the half-angle identity cos2x=12(1+cos2x)\displaystyle {{\cos}^{{2}}{x}}=\frac{{1}}{{2}}{\left({1}+{\cos{{2}}}{x}\right)}

solution = + C