Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 5 - Section 5.3 - Double-Angle, Power-Reducing, and Half-Angle Formulas - Exercise Set - Page 681: 75

Answer

See the explanation below.

Work Step by Step

We use the trigonometric identity: ${{\csc }^{2}}x=\frac{1}{{{\sin }^{2}}x}$ and $\cot x=\frac{\cos x}{\sin x}$. Now, the left side can be written as: $\begin{align} & \frac{{{\csc }^{2}}x}{\cot x}=\frac{\left( \frac{1}{{{\sin }^{2}}x} \right)}{\left( \frac{\cos x}{\sin x} \right)} \\ & =\frac{1}{{{\sin }^{2}}x}\times \frac{\sin x}{\cos x} \\ & =\frac{1}{\sin x\cos x} \\ & =\frac{2}{2\sin x\cos x} \end{align}$ Next, we use the trigonometric identities: $2\sin x\cos x=\sin 2x$ and $\frac{1}{\sin x}=\csc x$ Simplified further, $\begin{align} & \frac{2}{2\sin x\cos x}=\frac{2}{\sin 2x} \\ & =2\csc x \end{align}$ Thus, the left side of the equation is equal to $2\csc x$. Hence, the left side is equal to $2\csc x$.
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