Hãy tìm (I = int {dfrac{{{{cos }^3}x}}{{1 + sin x}},dx} ).

Ta có:

(I = int {dfrac{{{{cos }^3}x}}{{1 + sin x}},dx} )

(= int {dfrac{{{{cos }^2}x}}{{1 + sin x}}} ,dleft( {sin x} right) )

(= int {dfrac{{1 – {{sin }^2}x}}{{1 + sin x}}} ,dleft( {sin x} right))

( = int {left( {1 – sin x} right)} ,dleft( {sin x} right) )

(= left( {sin x – dfrac{1}{2}{{sin }^2}x} right) + C)

Chọn đáp án A.