1.

If `overset(a)underset(0)int(1)/(1+4x^(2))dx=(pi)/(8)`, then a equalsA. `(1)/(4)`B. `-(1)/(2)`C. `(3)/(2)`D. `(1)/(2)`

Answer» Correct Answer - D
Given , ` int _(0)^(p) (dx)/(1+4x^(2))= pi/8` ,
` LHS = int _(0)^(p) (dx)/(1+4x^(2)) = 1/4 int _(0)^(p) (dx)/(1/4+x^(2)) = 1/4 xx (1)/(1/2) [ tan^(-1)(x/(1/2))]_(0)^(p)`
` rArr 1/2 (tan^(-1) 2p ) = pi/8`
` rArr tan^(-1) 2p = pi/4 rArr 2p = 1`
` rArr p = 1/2`


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