Question

If $f ^ { \prime } ( 1 )$ is

• A. Zero
• B. 2/3
• C. $- 1$
• D. 1

Answer 1

Answer: (D)

1

Answer 2

Given $= 2 \tan ^ { - 1 } t$

Differentiating with respect to t, $f ^ { \prime } ( t ) = \frac { 2 } { 1 + t ^ { 2 } }$

⇒ $f ^ { \prime } ( 1 ) = \frac { 2 } { 2 } = 1$ .