Tích phân hàm lẻ kiểu j cũng $=0$
Đặt $x=-t \Rightarrow dx=-dt$
$I=\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} \sin^5 (-t) dt = -\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} \sin^5 t dt = \int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} \sin^5 x dx = -I$
$\Rightarrow 2I = 0 \Rightarrow I = 0$