Write the product as a sum: 18 sin(38z) sin(23z) =

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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**Write the product as a sum:**

\( 18 \sin(38z) \sin(23z) = \) 

---

To solve this, we use the product-to-sum identities for sine functions. The identity for the product of sines is:

\[
\sin A \sin B = \frac{1}{2} [\cos(A-B) - \cos(A+B)]
\]

Applying this identity to \( \sin(38z) \sin(23z) \):

Let \( A = 38z \) and \( B = 23z \).

\[
\sin(38z) \sin(23z) = \frac{1}{2} [\cos((38z) - (23z)) - \cos((38z) + (23z))]
\]

\[
= \frac{1}{2} [\cos(15z) - \cos(61z)]
\]

Now multiply by 18:

\[
18 \sin(38z) \sin(23z) = 18 \times \frac{1}{2} [\cos(15z) - \cos(61z)]
\]

\[
= 9 [\cos(15z) - \cos(61z)]
\]

The solution is:

\[
9 \cos(15z) - 9 \cos(61z)
\]
Transcribed Image Text:**Write the product as a sum:** \( 18 \sin(38z) \sin(23z) = \) --- To solve this, we use the product-to-sum identities for sine functions. The identity for the product of sines is: \[ \sin A \sin B = \frac{1}{2} [\cos(A-B) - \cos(A+B)] \] Applying this identity to \( \sin(38z) \sin(23z) \): Let \( A = 38z \) and \( B = 23z \). \[ \sin(38z) \sin(23z) = \frac{1}{2} [\cos((38z) - (23z)) - \cos((38z) + (23z))] \] \[ = \frac{1}{2} [\cos(15z) - \cos(61z)] \] Now multiply by 18: \[ 18 \sin(38z) \sin(23z) = 18 \times \frac{1}{2} [\cos(15z) - \cos(61z)] \] \[ = 9 [\cos(15z) - \cos(61z)] \] The solution is: \[ 9 \cos(15z) - 9 \cos(61z) \]
Expert Solution
Step 1

The given expression is:

18sin(38z)sin(23z)...(1)

Note that the formula used is:

2sin α cos β=cos(α-β)-cos(α+β)

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