Find dx 11 for y = 9x2 sin x + 18x cos x – 18 sin x. dx

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...
Question
**Problem Statement**

Find \(\frac{dy}{dx}\) for the function:

\[ y = 9x^2 \sin x + 18x \cos x - 18 \sin x \]

---

**Solution**

To find \(\frac{dy}{dx}\), we need to differentiate each term in the function \( y \).

1. Differentiate \( y = 9x^2 \sin x \):

   Apply the product rule: If \( u = 9x^2 \) and \( v = \sin x \), then

   \[
   \frac{d}{dx}[uv] = u'v + uv'
   \]

   - \( u' = \frac{d}{dx}(9x^2) = 18x \)
   - \( v' = \frac{d}{dx}(\sin x) = \cos x \)

   So, 

   \[
   \frac{d}{dx}(9x^2 \sin x) = 18x \sin x + 9x^2 \cos x
   \]

2. Differentiate \( y = 18x \cos x \):

   Again, apply the product rule: If \( u = 18x \) and \( v = \cos x \), then

   \[
   \frac{d}{dx}[uv] = u'v + uv'
   \]

   - \( u' = \frac{d}{dx}(18x) = 18 \)
   - \( v' = \frac{d}{dx}(\cos x) = -\sin x \)

   So, 

   \[
   \frac{d}{dx}(18x \cos x) = 18 \cos x - 18x \sin x
   \]

3. Differentiate \( y = -18 \sin x \):

   - The derivative of \(-18 \sin x\) is \(-18 \cos x\).

Combine these results:

\[
\frac{dy}{dx} = (18x \sin x + 9x^2 \cos x) + (18 \cos x - 18x \sin x) - 18 \cos x 
\]

Simplify the expression:

\[
\frac{dy}{dx} = 9x^2 \cos x 
\]

Therefore, the derivative of the
Transcribed Image Text:**Problem Statement** Find \(\frac{dy}{dx}\) for the function: \[ y = 9x^2 \sin x + 18x \cos x - 18 \sin x \] --- **Solution** To find \(\frac{dy}{dx}\), we need to differentiate each term in the function \( y \). 1. Differentiate \( y = 9x^2 \sin x \): Apply the product rule: If \( u = 9x^2 \) and \( v = \sin x \), then \[ \frac{d}{dx}[uv] = u'v + uv' \] - \( u' = \frac{d}{dx}(9x^2) = 18x \) - \( v' = \frac{d}{dx}(\sin x) = \cos x \) So, \[ \frac{d}{dx}(9x^2 \sin x) = 18x \sin x + 9x^2 \cos x \] 2. Differentiate \( y = 18x \cos x \): Again, apply the product rule: If \( u = 18x \) and \( v = \cos x \), then \[ \frac{d}{dx}[uv] = u'v + uv' \] - \( u' = \frac{d}{dx}(18x) = 18 \) - \( v' = \frac{d}{dx}(\cos x) = -\sin x \) So, \[ \frac{d}{dx}(18x \cos x) = 18 \cos x - 18x \sin x \] 3. Differentiate \( y = -18 \sin x \): - The derivative of \(-18 \sin x\) is \(-18 \cos x\). Combine these results: \[ \frac{dy}{dx} = (18x \sin x + 9x^2 \cos x) + (18 \cos x - 18x \sin x) - 18 \cos x \] Simplify the expression: \[ \frac{dy}{dx} = 9x^2 \cos x \] Therefore, the derivative of the
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