নির্দিষ্ট যোগজ

The value of ;0π/4secx(secx+tanx)2dx\displaystyle \int_{0}^{\pi /4}\frac{\sec x}{\left ( \sec x+\tan x \right )^{2}}dx is& ;

হানি নাটস

Let I=0π4secx(secx+tanx)2dx\displaystyle I=\int _{ 0 }^{ \dfrac { \pi }{ 4 } }{ \frac { \sec { x } }{ { \left( \sec { x } +\tan { x } \right) }^{ 2 } } } dx

Multiply numerator and denominator by cos2x\cos ^{ 2 }{ x } , we get

I=0121(u+1)2du=[1u+1]012\displaystyle I=\int _{ 0 }^{ \dfrac { 1 }{ \sqrt { 2 } } }{ \dfrac { 1 }{ { \left( u+1 \right) }^{ 2 } } } du=\left[ \dfrac { -1 }{ u+1 } \right] _{ 0 }^{ \dfrac { 1 }{ \sqrt { 2 } } }

=112+1\displaystyle =-\dfrac { 1 }{ \dfrac { 1 }{ \sqrt { 2 } } +1 }

=21+2=\dfrac { -\sqrt { 2 } }{ 1+\sqrt { 2 } }

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