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 683: 118

Answer

The required solution is True.

Work Step by Step

Let us consider the left side of the given expression: $sin\pi \cos \frac{\pi }{2}$ Then, put the values of the trigonometric functions to find the exact value as shown below: $\begin{align} & sin\pi \cos \frac{\pi }{2}=0\cdot 0 \\ & =0 \end{align}$ Also, consider the right side of the given expression: $\frac{1}{2}\left[ \sin \left( \pi +\frac{\pi }{2} \right)+\sin \left( \pi -\frac{\pi }{2} \right) \right]$ Now, put the values of the trigonometric functions to find the exact value as shown below: $\begin{align} & \frac{1}{2}\left[ \sin \left( \pi +\frac{\pi }{2} \right)+\sin \left( \pi -\frac{\pi }{2} \right) \right]=\frac{1}{2}\left[ \sin \left( \frac{2\pi +\pi }{2} \right)+\sin \left( \frac{2\pi -\pi }{2} \right) \right] \\ & =\frac{1}{2}\left[ \sin \left( \frac{3\pi }{2} \right)+\sin \left( \frac{\pi }{2} \right) \right] \\ & =\frac{1}{2}\left[ -1+1 \right] \\ & =0 \end{align}$ So, the left side of the expression is equal to the right side, which is $sin\pi \cos \frac{\pi }{2}=\frac{1}{2}\left[ \sin \left( \pi +\frac{\pi }{2} \right)+\sin \left( \pi -\frac{\pi }{2} \right) \right]$.
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