Tìm (I = int {frac{{{{cos }^3}x}}{{1 + sin x}}dx} )

Đặt (t = sin x Rightarrow dt = cos xdx)

(I = int {frac{{left( {1 – {t^2}} right)}}{{1 + t}}dt}  = int {left( {1 – t} right)} dt =  – frac{{{t^2}}}{2} + t =  – frac{{{{sin }^2}x}}{2} + sin x + C)