Math Problem Statement

let f(x) be a differentiable function and f^(-1) (x) be its inverse function. let g(x) = 2f(x) + (f^-1(x))^2. it is given that f(1) =1 and f'(1) = 1/2. find the value of g'(1)

Solution

To find g(1)g'(1), we need to differentiate the function g(x)=2f(x)+(f1(x))2g(x) = 2f(x) + (f^{-1}(x))^2. Given that f(x)f(x) is differentiable and f1(x)f^{-1}(x) is its inverse, let's go through the differentiation step-by-step.

Step 1: Differentiate g(x)g(x)

The function g(x)g(x) is defined as: g(x)=2f(x)+(f1(x))2.g(x) = 2f(x) + \left(f^{-1}(x)\right)^2. We need to find g(x)g'(x). Using the sum rule, we differentiate each part separately: g(x)=2f(x)+2f1(x)ddx[f1(x)].g'(x) = 2f'(x) + 2f^{-1}(x) \cdot \frac{d}{dx}[f^{-1}(x)].

Step 2: Differentiate f1(x)f^{-1}(x)

The derivative of the inverse function f1(x)f^{-1}(x) is given by: ddx[f1(x)]=1f(f1(x)).\frac{d}{dx}[f^{-1}(x)] = \frac{1}{f'\left(f^{-1}(x)\right)}. So, the expression for g(x)g'(x) becomes: g(x)=2f(x)+2f1(x)1f(f1(x)).g'(x) = 2f'(x) + 2f^{-1}(x) \cdot \frac{1}{f'\left(f^{-1}(x)\right)}.

Step 3: Evaluate g(1)g'(1)

We need to find g(1)g'(1). First, we need to determine f1(1)f^{-1}(1). Since f(1)=1f(1) = 1, by the property of inverse functions, f1(1)=1f^{-1}(1) = 1.

Now substitute x=1x = 1 into the derivative: g(1)=2f(1)+2f1(1)1f(f1(1)).g'(1) = 2f'(1) + 2f^{-1}(1) \cdot \frac{1}{f'\left(f^{-1}(1)\right)}. Substitute the values f(1)=12f'(1) = \frac{1}{2} and f1(1)=1f^{-1}(1) = 1: g(1)=212+211f(1).g'(1) = 2 \cdot \frac{1}{2} + 2 \cdot 1 \cdot \frac{1}{f'(1)}. g(1)=1+2112.g'(1) = 1 + 2 \cdot \frac{1}{\frac{1}{2}}. g(1)=1+22.g'(1) = 1 + 2 \cdot 2. g(1)=1+4=5.g'(1) = 1 + 4 = 5.

Thus, the value of g(1)g'(1) is 55.

Would you like more details or have any questions?

Here are 5 related questions for further exploration:

  1. What is the geometric interpretation of the derivative of an inverse function?
  2. How can the inverse function theorem be applied in different contexts?
  3. What happens to g(x)g'(x) if f(x)f(x) is not differentiable at some point?
  4. How does the chain rule apply when differentiating composite functions involving inverse functions?
  5. How do you find the inverse of more complex functions analytically?

Tip: When working with inverse functions, remember that (f1)(x)=1f(f1(x))(f^{-1})'(x) = \frac{1}{f'(f^{-1}(x))}. This is a crucial identity for differentiating expressions involving inverses.

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Math Problem Analysis

Mathematical Concepts

Differentiation
Inverse Functions
Chain Rule
Derivative of Inverse Function

Formulas

g(x) = 2f(x) + (f^{-1}(x))^2
g'(x) = 2f'(x) + 2f^{-1}(x) * (1 / f'(f^{-1}(x)))
(f^{-1})'(x) = 1 / f'(f^{-1}(x))

Theorems

Inverse Function Theorem
Chain Rule

Suitable Grade Level

University (Calculus I/II level)