question_answer

\[\int{\cos \left. \left\{ 1\,\,{{\tan }^{-1}}\sqrt{\frac{1-x}{1+x}} \right. \right\}}dx=\]

A)  \[\frac{1}{2}{{x}^{2}}+C\]   

B)  \[\frac{1}{8}\left( {{x}^{2}}-1 \right)+C\]

C)  \[\frac{1}{2}x+C\]       

D)  None of these