Trigonometry (11th Edition)
Trigonometry (11th Edition)
11th Edition
ISBN: 9780134217437
Author: Margaret L. Lial, John Hornsby, David I. Schneider, Callie Daniels
Publisher: PEARSON
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Question
Prove the identity.

\[
\frac{\sin(2x)}{1 + \tan^2(x)} = \frac{2 \tan(x)}{1 + \tan^2(x)}
\]

Write the more complicated side of the equation in terms of \(\sin(x)\) and \(\cos(x)\). Simplify the complex fraction.

\[
\frac{2 \tan(x)}{1 + \tan^2(x)} = \frac{2 \cdot \frac{\sin(x)}{\cos(x)}}{1 + \frac{\sin(x)}{\cos^2(x)}}
\]

\[
= \frac{2 \cdot \frac{\sin(x)}{\cos(x)}}{1 + \frac{\sin^2(x)}{\cos^2(x)}}
\]

Marked with a green check (\(\sin(x)/\cos(x)\)) indicates correct steps, while red crosses indicate incorrect placements or notations.

\[
= \frac{2 \cdot \frac{\sin(x)}{\cos(x)}}{\cos^2(x)/\sin^2(x)}
\]

\[
= \frac{2 \cdot \sin(x) \cdot \cos(x)}{\cos^2(x) + \sin^2(x)}
\]

\[
= \frac{2 \sin(x) \cos(x)}{1}
\]

\[
= \sin(2x)
\]

In this solution, the identity for \(\sin(2x) = 2 \sin(x) \cos(x)\) is used to simplify and confirm the trigonometric identity.
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Transcribed Image Text:Prove the identity. \[ \frac{\sin(2x)}{1 + \tan^2(x)} = \frac{2 \tan(x)}{1 + \tan^2(x)} \] Write the more complicated side of the equation in terms of \(\sin(x)\) and \(\cos(x)\). Simplify the complex fraction. \[ \frac{2 \tan(x)}{1 + \tan^2(x)} = \frac{2 \cdot \frac{\sin(x)}{\cos(x)}}{1 + \frac{\sin(x)}{\cos^2(x)}} \] \[ = \frac{2 \cdot \frac{\sin(x)}{\cos(x)}}{1 + \frac{\sin^2(x)}{\cos^2(x)}} \] Marked with a green check (\(\sin(x)/\cos(x)\)) indicates correct steps, while red crosses indicate incorrect placements or notations. \[ = \frac{2 \cdot \frac{\sin(x)}{\cos(x)}}{\cos^2(x)/\sin^2(x)} \] \[ = \frac{2 \cdot \sin(x) \cdot \cos(x)}{\cos^2(x) + \sin^2(x)} \] \[ = \frac{2 \sin(x) \cos(x)}{1} \] \[ = \sin(2x) \] In this solution, the identity for \(\sin(2x) = 2 \sin(x) \cos(x)\) is used to simplify and confirm the trigonometric identity.
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