prove this $\int{sin^3xcos^nx}d(x)=\frac{2}{3+n}\int sinxcos^nxd(x)-\frac{sin^2xcos^{n+1}x}{3+n}$ In this problem i write $sin^3x$ like this $sin^3x=\frac{3sinx-sin3x}{4}$after that i use $\int u \frac{d(v)}{d(x)}$ format and after that i get stucked and i get everything in cos.please give me a solution??