lam ho^. em ca^u nay` em nap. cho 100K

A

alreay_dead

[TEX]I=\int_{0}^{\pi/4} x.tan^2xdx[/TEX]
Đặt [TEX]\left{\begin{u=x}\\{dv=tan^2xdx}[/TEX] [TEX]\Rightarrow\left{\begin{du=dx}\\{v=tanx-x}[/TEX]
[TEX]I=x(tanx-x)|^{\pi/4}_{0}-\int_{0}^{\pi/4}(tanx-x)dx[/TEX]
Dễ dàng tính được [TEX]I=\frac{\pi}{4}-\frac{\pi^2}{32}-ln\sqrt{2}[/TEX]
 
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