The below integral can be evaluated using two different methods: $$sin$^2($x$)$ cos$^2($x$)$ dx $.$ Method $1$: Use power reducing formulas to rewrite the integrand, More than one application of the power$-$reducing formulas is needed $($each will use doubling of the angle$).$ When no powers of sin$/$cosine are greater than $1,$ you are ready to integrate, substitution may be needed.