1.

The value of integral `int_(0)^(1)sqrt((1-x)/(1+x))`dx isA. `(pi)/(2)+1`B. `(pi)/(2)-1`C. `-1`D. 1

Answer» Correct Answer - B
Let ` l = int_(0)^(1) sqrt((1-x)/(1+x))`
Put `x = cos 2 theta rArr dx = -2 sin 2 theta d theta`
` :. l = int_(pi//4)^(0) sqrt((1- cos 2 theta)/(1+cos 2theta)) . 2 sin 2 theta d theta `
` = 2 int _(0)^(pi//4) (sin theta)/(cos theta) . 2 sin theta cos theta d theta`
` = 2 int_(0)^(pi//4) (1+ cos 2 theta) d theta = 2 [ theta - (sin 2 theta)/2 ] _(0)^(pi//4) = pi/2 -1 `


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