$\int \operatorname{Cos}^{-1}\left(\frac{1-x^2}{1+x^2}\right) d x=$

• Correct answer
  A

  $2\left[x \operatorname{Tan}^{-1} x-\log \sqrt{1+x^2}\right]+c$
• B

  $2x \operatorname{Tan}^{-1} x+\log \sqrt{1-x^2}+c$
• C

  $x \operatorname{Tan}^{-1} x+\log \sqrt{1-x^2}+c$
• D

  $2\left[\operatorname{Tan}^{-1} x-\log \sqrt{1+x^2}\right]+c$

Hence, the correct answer is option: 'A'.