Find given sin(3x)cos(x). dx

Calculus: Early Transcendentals
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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 Trigonometric Function**

**Problem Statement:**

Find \(\frac{dy}{dx}\) given \( \sin(3x)\cos(x) \).

**Solution Steps:**

To find \(\frac{dy}{dx}\) for the given function \(y = \sin(3x)\cos(x)\), we can utilize the product rule for differentiation. The product rule states that if \(u(x)\) and \(v(x)\) are functions of \(x\), then the derivative of their product is given by:

\[
\frac{d}{dx}[u(x)v(x)] = u'(x)v(x) + u(x)v'(x)
\]

Let \(u(x) = \sin(3x)\) and \(v(x) = \cos(x)\).

First, compute the derivatives of each function:

1. \(u(x) = \sin(3x)\)
   \(u'(x) = \frac{d}{dx}[\sin(3x)] = 3\cos(3x)\) (using the chain rule)

2. \(v(x) = \cos(x)\)
   \(v'(x) = \frac{d}{dx}[\cos(x)] = -\sin(x)\)

Now apply the product rule:

\[
\frac{dy}{dx} = u'(x)v(x) + u(x)v'(x)
\]

Substitute \(u'(x)\), \(u(x)\), \(v(x)\), and \(v'(x)\):

\[
\frac{dy}{dx} = [3\cos(3x)] \cos(x) + [\sin(3x)] [-\sin(x)] 
\]

Simplify the expression:

\[
\frac{dy}{dx} = 3\cos(3x)\cos(x) - \sin(3x)\sin(x)
\]

Therefore, the derivative of \(y = \sin(3x)\cos(x)\) is:

\[
\frac{dy}{dx} = 3\cos(3x)\cos(x) - \sin(3x)\sin(x)
\]

This is the required derivative.
Transcribed Image Text:**Calculus Problem: Derivative of Trigonometric Function** **Problem Statement:** Find \(\frac{dy}{dx}\) given \( \sin(3x)\cos(x) \). **Solution Steps:** To find \(\frac{dy}{dx}\) for the given function \(y = \sin(3x)\cos(x)\), we can utilize the product rule for differentiation. The product rule states that if \(u(x)\) and \(v(x)\) are functions of \(x\), then the derivative of their product is given by: \[ \frac{d}{dx}[u(x)v(x)] = u'(x)v(x) + u(x)v'(x) \] Let \(u(x) = \sin(3x)\) and \(v(x) = \cos(x)\). First, compute the derivatives of each function: 1. \(u(x) = \sin(3x)\) \(u'(x) = \frac{d}{dx}[\sin(3x)] = 3\cos(3x)\) (using the chain rule) 2. \(v(x) = \cos(x)\) \(v'(x) = \frac{d}{dx}[\cos(x)] = -\sin(x)\) Now apply the product rule: \[ \frac{dy}{dx} = u'(x)v(x) + u(x)v'(x) \] Substitute \(u'(x)\), \(u(x)\), \(v(x)\), and \(v'(x)\): \[ \frac{dy}{dx} = [3\cos(3x)] \cos(x) + [\sin(3x)] [-\sin(x)] \] Simplify the expression: \[ \frac{dy}{dx} = 3\cos(3x)\cos(x) - \sin(3x)\sin(x) \] Therefore, the derivative of \(y = \sin(3x)\cos(x)\) is: \[ \frac{dy}{dx} = 3\cos(3x)\cos(x) - \sin(3x)\sin(x) \] This is the required derivative.
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