Integral Calculus Question 494

Question: $ \int{\sqrt{\frac{1+x}{1-x}}dx=} $

[RPET 2002]

Options:

A) $ -{{\sin }^{-1}}x-\sqrt{1-x^{2}},+c $

B) $ {{\sin }^{-1}}x+\sqrt{1-x^{2}},+c $

C) $ {{\sin }^{-1}}x-\sqrt{1-x^{2}},+c $

D) $ -{{\sin }^{-1}}x-\sqrt{x^{2}-1},+c $

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Answer:

Correct Answer: C

Solution:

$ I=\int{\sqrt{\frac{1+x}{1-x}}dx} $ $ =\int{\frac{1+x}{\sqrt{1-x^{2}}}dx} $ $ =\int{\frac{dx}{\sqrt{1-x^{2}}}+\int{\frac{x}{\sqrt{1-x^{2}}}dx}} $ $ ={{\sin }^{-1}}x-\sqrt{1-x^{2}}+c $ .