JEE Main 2020 · MathsMultiple choiceSingle correctEasyApplication

JEE Main 9 January 2020, Shift 2, Maths Q60

Question 60 of 75 in this shift, Maths question 10 of 25, Section A.

Let

f

and

g

be differentiable functions on

\mathbf{R}

such that

f\circ g

is the identity function. If for some

a,b\in\mathbf{R}

g'(a)=5

and

g(a)=b

, then

f'(b)

is equal to :

(1) $\frac{1}{5}$ Official answer
(2) $\frac{2}{5}$
(3) $1$
(4) $5$

Official answer

Option 1

NTA final key (Jan 2020).

Chapter: Continuity and Differentiability
Topic: Chain Rule
Idea tested: Derivative of Inverse Functions via Chain Rule

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Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.