Consider the following statements Assertion (A): For $x \in \mathbb{R}-\{1\}, \frac{d}{d x}\left(\operatorname{Tan}^{-1}\left(\frac{1+x}{1-x}\right)\right)=\frac{d}{d x}\left(\operatorname{Tan}^{-1} x\right)$ Reason (R): For $x < 1, \operatorname{Tan}^{-1}\left(\frac{1+x}{1-x}\right)=\frac{\pi}{4}+\operatorname{Tan}^{-1} x$, for $x>1, \operatorname{Tan}^{-1}\left(\frac{1+x}{1-x}\right)=-\frac{3 \pi}{4}+\operatorname{Tan}^{-1} x$ The correct answer is

• Correct answer
  A

  Both (A) and (R) are true, (R) is the correct explanation of (A)
• B

  Both (A) and (R) are true, (R) is not the correct explanation of (A)
• C

  (A) is true, but (R) is false
• D

  (A) is false, but (R) is true

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