Trigonometry (10th Edition)

Published by Pearson
ISBN 10: 0321671775
ISBN 13: 978-0-32167-177-6

Chapter 5 - Trigonometric Identities - Section 5.2 Verifying Trigonometric Identities - 5.2 Exercises - Page 202: 35

Answer

$$\frac{\cot\theta}{\csc\theta}=\cos\theta$$ The identity is proved by simplifying the left side.

Work Step by Step

$$\frac{\cot\theta}{\csc\theta}=\cos\theta$$ Seeing that the left side is more complicated, we would simplify it, using the following identities $$\cot\theta=\frac{\cos\theta}{\sin\theta}$$ $$\csc\theta=\frac{1}{\sin\theta}$$ Therefore, the left side now would be $$\frac{\cot\theta}{\csc\theta}=\frac{\frac{\cos\theta}{\sin\theta}}{\frac{1}{\sin\theta}}$$ $$=\frac{\cos\theta\sin\theta}{\sin\theta}$$ $$=\cos\theta$$ The identity is hence proved.
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