নির্দিষ্ট যোগজ

0π/4(tan3x+tanx)dx\int_{0}^{\pi / 4}\left(\tan ^{3} x+\tan x\right) d x

Solve:

0π/4(tan3x+tanx)dx=0π/4(tan2x+1)tanxdx \begin{array}{l} \int_{0}^{\pi / 4}\left(\tan ^{3} x+\tan x\right) d x \\ =\int_{0}^{\pi / 4}\left(\tan ^{2} x+1\right) \tan x d x \end{array}

=0π/4sec2xtanxdx=0π/4(tanx)d(tanx)=[12(tanx)2]0π/4=12{(tanπ4)2(tan0)2}=12{(1)20}=12 \begin{array}{l} =\int_{0}^{\pi / 4} \sec ^{2} x \tan x d x \\ =\int_{0}^{\pi / 4}(\tan x) d(\tan x)=\left[\frac{1}{2}(\tan x)^{2}\right]_{0}^{\pi / 4} \\ =\frac{1}{2}\left\{\left(\tan \frac{\pi}{4}\right)^{2}-(\tan 0)^{2}\right\}=\frac{1}{2}\left\{(1)^{2}-0\right\}=\frac{1}{2} \end{array}

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