## Precalculus (6th Edition) Blitzer

Published by Pearson

# Chapter 4 - Section 4.5 - Graphs of Sine and Cosine Functions - Exercise Set - Page 595: 9

#### Answer

The amplitude and period of the function are $3$ and $4\pi$ , respectively.

#### Work Step by Step

We have the trigonometric function $y=3\sin \frac{1}{2}x$ The amplitude is the maximum value of $y$. The maximum value of the given trigonometric function is $3$. So, the amplitude of the trigonometric function is $3$. The function after a certain interval starts repeating itself, and this interval is known as the period of the function. And the period $\left( B \right)$ of the trigonometric function is \begin{align} & B=\frac{2\pi }{\left( \frac{1}{2} \right)} \\ & =4\pi \end{align} And the quarter period is $\frac{4\pi }{4}$ or $\pi$. The cycle begins at $x=0$. Add quarter periods to find out the key points. First key point is ${{x}_{1}}=0$ Second key point is \begin{align} & {{x}_{2}}=0+\pi \\ & =\pi \end{align} Third key point is \begin{align} & {{x}_{3}}=\pi +\pi \\ & =2\pi \end{align} Fourth key point is \begin{align} & {{x}_{4}}=2\pi +\pi \\ & =3\pi \end{align} Fifth key point is \begin{align} & {{x}_{5}}=3\pi +\pi \\ & =4\pi \end{align}

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