1.

` int _(0)^(a) (xdx)/(sqrt(a^(2)+x^(2)) )` is equal toA. `a(sqrt2-1)`B. `a(1-sqrt2)`C. `a(1+sqrt2)`D. `2asqrt3`

Answer» Correct Answer - A
Put ` t = a^(2) +x^(2) rArr 2xdx = dt`
` :. int _(0)^(a) (xdx)/(sqrt(a^(2)+x^(2)) )= 1/2 int _(a^(2))^(2a^(2)) 1/(sqrt(t)) dt `
` = [ ( 2a^(2) )^(1/2) - a^(2/2)]= a (sqrt(2)-1)`


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