Find the derivative of y = In (tanh x).

Calculus: Early Transcendentals
8th Edition
ISBN:9781285741550
Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
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## Calculus Problem: Derivative of a Logarithmic Hyperbolic Function

### Problem Statement:
Find the derivative of \( y = \ln(\tanh(x)) \).

### Solution Approach:

To find the derivative of \( y = \ln(\tanh(x)) \), we will use the chain rule.

1. **Identify the Outer and Inner Functions**:
   Our function is a composition of two functions:
   - Outer function: \( u = \ln(u) \)
   - Inner function: \( u = \tanh(x) \)

2. **Differentiate the Outer Function with respect to the Inner Function**:
   Differentiating \( \ln(u) \) with respect to \( u \), we get:
   \[
   \frac{d}{du} \ln(u) = \frac{1}{u}
   \]

3. **Differentiate the Inner Function with respect to \( x \)**:
   Differentiating \( \tanh(x) \) with respect to \( x \), we have:
   \[
   \frac{d}{dx} \tanh(x) = 1 - \tanh^2(x)
   \]

4. **Combine Using the Chain Rule**:
   By the chain rule, the derivative of \( y = \ln(\tanh(x)) \) with respect to \( x \) is:
   \[
   \frac{dy}{dx} = \frac{d}{du} \ln(u) \cdot \frac{du}{dx} = \frac{1}{\tanh(x)} \cdot (1 - \tanh^2(x))
   \]

5. **Simplify the Result**:
    Therefore, the derivative is:
   \[
   \frac{dy}{dx} = \frac{1 - \tanh^2(x)}{\tanh(x)}
   \]

Thus, the derivative is:
\[
\boxed{\frac{dy}{dx} = \frac{1 - \tanh^2(x)}{\tanh(x)}}
\]

This result gives us the rate of change of the function \( y = \ln(\tanh(x)) \) with respect to \( x \).

---

This problem illustrates the application of the chain rule in differentiation, specifically dealing with logarithmic and hyperbolic functions.
Transcribed Image Text:## Calculus Problem: Derivative of a Logarithmic Hyperbolic Function ### Problem Statement: Find the derivative of \( y = \ln(\tanh(x)) \). ### Solution Approach: To find the derivative of \( y = \ln(\tanh(x)) \), we will use the chain rule. 1. **Identify the Outer and Inner Functions**: Our function is a composition of two functions: - Outer function: \( u = \ln(u) \) - Inner function: \( u = \tanh(x) \) 2. **Differentiate the Outer Function with respect to the Inner Function**: Differentiating \( \ln(u) \) with respect to \( u \), we get: \[ \frac{d}{du} \ln(u) = \frac{1}{u} \] 3. **Differentiate the Inner Function with respect to \( x \)**: Differentiating \( \tanh(x) \) with respect to \( x \), we have: \[ \frac{d}{dx} \tanh(x) = 1 - \tanh^2(x) \] 4. **Combine Using the Chain Rule**: By the chain rule, the derivative of \( y = \ln(\tanh(x)) \) with respect to \( x \) is: \[ \frac{dy}{dx} = \frac{d}{du} \ln(u) \cdot \frac{du}{dx} = \frac{1}{\tanh(x)} \cdot (1 - \tanh^2(x)) \] 5. **Simplify the Result**: Therefore, the derivative is: \[ \frac{dy}{dx} = \frac{1 - \tanh^2(x)}{\tanh(x)} \] Thus, the derivative is: \[ \boxed{\frac{dy}{dx} = \frac{1 - \tanh^2(x)}{\tanh(x)}} \] This result gives us the rate of change of the function \( y = \ln(\tanh(x)) \) with respect to \( x \). --- This problem illustrates the application of the chain rule in differentiation, specifically dealing with logarithmic and hyperbolic functions.
### Problem Statement:
Evaluate the integral of the hyperbolic tangent function \( \tanh(3x) \).

### Mathematical Expression:
\[
\int \tanh(3x) \, dx
\]
Transcribed Image Text:### Problem Statement: Evaluate the integral of the hyperbolic tangent function \( \tanh(3x) \). ### Mathematical Expression: \[ \int \tanh(3x) \, dx \]
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