1.

` int _(0)^(1) (dx)/(1+x+x^(2))` is equal toA. `(pi)/(sqrt3)`B. `(pi)/(2sqrt3)`C. `(2pi)/(3sqrt3)`D. `(pi)/(3sqrt3)`

Answer» Correct Answer - D
`int_(0)^(1) (dx)/(1+x+x^(2)) = int_(0)^(1) (dx)/(x^(2) + x + 1/4 - 1/4 +1 )`
` = int _(0)^(1) (dx)/((x+1/2)^(2)+ ((sqrt(3))/2)^(2))` ,
` = 2/(sqrt(3)) [ tan^(-1). ((x+1/2))/(sqrt(3)/2)]_(0)^(1)`
` = 2/(sqrt(3)) [ tan^(-1) ((3/2)/(sqrt(3)/2))-tan^(-1) ((1/2)/(sqrt(3)/2))]`
` = 2/(sqrt(3)) [ tan^(-1) sqrt(3) - tan ^(-1). 1/(sqrt(3))]`
` =2/(sqrt(3)) (pi/3 - pi/6) = (2pi)/(6sqrt(3)) = pi/(3sqrt(3))`


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