Use logarithmic differentiation

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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**Logarithmic Differentiation Example**

**Problem:** Use logarithmic differentiation to find \( y' \) if \( y = (\cos x)^{\cos x} \).

**Solution:**

To differentiate the function \( y = (\cos x)^{\cos x} \), we will use the method of logarithmic differentiation. This technique is especially useful when dealing with functions that are powers of other functions.

1. **Take the natural logarithm of both sides:**

   \[
   \ln y = \ln \left( (\cos x)^{\cos x} \right)
   \]

2. **Simplify using logarithm properties:**

   The property \(\ln(a^b) = b \ln a\) gives us:

   \[
   \ln y = \cos x \cdot \ln (\cos x)
   \]

3. **Differentiate both sides with respect to \( x \):**

   The left side becomes \(\frac{1}{y} \cdot \frac{dy}{dx}\). For the right side, apply the product rule to \(\cos x \cdot \ln (\cos x)\):

   \[
   \frac{1}{y} \cdot \frac{dy}{dx} = \left(-\sin x\right) \ln (\cos x) + \frac{-\sin x}{\cos x} \cos x
   \]

   Simplify the equation:

   \[
   \frac{1}{y} \cdot \frac{dy}{dx} = -\sin x \cdot \ln (\cos x) - \sin x
   \]

4. **Solve for \( \frac{dy}{dx} \):**

   Multiply both sides by \( y \) (which is \( (\cos x)^{\cos x} \)):

   \[
   \frac{dy}{dx} = (\cos x)^{\cos x} \left( -\sin x \cdot \ln (\cos x) - \sin x \right)
   \]

Therefore, the derivative \( y' \) is:

\[
y' = - (\cos x)^{\cos x} \cdot \sin x \cdot \left( \ln (\cos x) + 1 \right)
\]

This solution demonstrates the application of logarithmic differentiation to find
Transcribed Image Text:**Logarithmic Differentiation Example** **Problem:** Use logarithmic differentiation to find \( y' \) if \( y = (\cos x)^{\cos x} \). **Solution:** To differentiate the function \( y = (\cos x)^{\cos x} \), we will use the method of logarithmic differentiation. This technique is especially useful when dealing with functions that are powers of other functions. 1. **Take the natural logarithm of both sides:** \[ \ln y = \ln \left( (\cos x)^{\cos x} \right) \] 2. **Simplify using logarithm properties:** The property \(\ln(a^b) = b \ln a\) gives us: \[ \ln y = \cos x \cdot \ln (\cos x) \] 3. **Differentiate both sides with respect to \( x \):** The left side becomes \(\frac{1}{y} \cdot \frac{dy}{dx}\). For the right side, apply the product rule to \(\cos x \cdot \ln (\cos x)\): \[ \frac{1}{y} \cdot \frac{dy}{dx} = \left(-\sin x\right) \ln (\cos x) + \frac{-\sin x}{\cos x} \cos x \] Simplify the equation: \[ \frac{1}{y} \cdot \frac{dy}{dx} = -\sin x \cdot \ln (\cos x) - \sin x \] 4. **Solve for \( \frac{dy}{dx} \):** Multiply both sides by \( y \) (which is \( (\cos x)^{\cos x} \)): \[ \frac{dy}{dx} = (\cos x)^{\cos x} \left( -\sin x \cdot \ln (\cos x) - \sin x \right) \] Therefore, the derivative \( y' \) is: \[ y' = - (\cos x)^{\cos x} \cdot \sin x \cdot \left( \ln (\cos x) + 1 \right) \] This solution demonstrates the application of logarithmic differentiation to find
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