Sign in
Please select an account to continue using cracku.in
↓ →
Join Our JEE Preparation Group
Prep with like-minded aspirants; Get access to free daily tests and study material.
If $$g$$ is the inverse of a function $$f$$ and $$f'(x) = \frac{1}{1+x^5}$$, then $$g'(x)$$ is equal to:
We wish to find the derivative of the inverse function. Let us denote the given function by $$y=f(x)$$ and its inverse by $$x=g(y)$$, so that $$g=f^{-1}$$.
Because $$g$$ and $$f$$ are inverses, we have the relation $$f\!\bigl(g(y)\bigr)=y$$ for every value of $$y$$ that lies in the domain of $$g$$.
Now we differentiate the identity $$f\!\bigl(g(y)\bigr)=y$$ with respect to $$y$$. Applying the chain rule, we obtain
$$f'\!\bigl(g(y)\bigr)\,\cdot\,g'(y)=1.$$
We want an explicit expression for $$g'(y)$$, so we solve for it algebraically. Dividing both sides by $$f'\!\bigl(g(y)\bigr)$$ we get
$$g'(y)=\frac{1}{f'\!\bigl(g(y)\bigr)}.$$
We now substitute the given derivative of $$f$$. According to the statement of the problem,
$$f'(x)=\frac{1}{1+x^{5}}.$$
Replacing the variable $$x$$ by $$g(y)$$ in this formula gives
$$f'\!\bigl(g(y)\bigr)=\frac{1}{1+\{g(y)\}^{5}}.$$
Substituting this result into our expression for $$g'(y)$$, we obtain
$$g'(y)=\frac{1}{\dfrac{1}{1+\{g(y)\}^{5}}}.$$
Simplifying the complex fraction (since dividing by a fraction is the same as multiplying by its reciprocal), we find
$$g'(y)=1+\{g(y)\}^{5}.$$
Because the independent variable in the final answer is conventionally written as $$x$$, we can replace $$y$$ by $$x$$ without changing the meaning:
$$g'(x)=1+\{g(x)\}^{5}.$$
This matches Option B in the list provided.
Hence, the correct answer is Option B.
Create a FREE account and get:
Predict your JEE Main percentile, rank & performance in seconds
Educational materials for JEE preparation
Ask our AI anything
AI can make mistakes. Please verify important information.
AI can make mistakes. Please verify important information.