1.

`intcos^(-1)((1-tan^(2)x)/(1+tan^(2)x)) dx = ?`A. `x^(2) + C`B. `-x^(2) + C`C. `1/(sqrt(1+x^(2))) + C`D. `1/(sqrt(1-x^(2))) + C`

Answer» Correct Answer - A
`cos^(-1)((1-tan^(2)x)/(1+ tanx^(2)x)) = cos^(-1) ((cos^(2)x - sin^(2)x)/(cos^(2)x + sin^(2)x))`
`= cos^(-1) (cos^(2)x - sin^(2)x) = cos^(-1) (cosx) = 2x`.


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