Let and be differentiable functions on such that fog is the identity function. If for some and , then is equal to:
- (A)1
- (B)5
- (C)✓ Correct
- (D)
Answer: (C)
Solution
Since is the identity, for all . Differentiating by the chain rule gives . Evaluating at , where and , this becomes , so .
JEE Main · 2020 · 09 Jan 2020 · Shift 2 · Single correct option