## Trigonometry (11th Edition) Clone

Published by Pearson

# Chapter 5 - Trigonometric Identities - Section 5.3 Sum and Difference Identities for Cosine - 5.3 Exercises - Page 220: 76a

#### Answer

$P = \frac{0.4}{10}~cos[\frac{(2\pi) (10)}{4.9}- 1026~t]$ We can see a sketch of the graph in the window $[0,0.05]$ by $[-0.05, 0.05]$ The sound pressure $P$ at a distance of ten feet from the source oscillates continuously between $0.04$ and $-0.04$

#### Work Step by Step

$P = \frac{a}{r}~cos(\frac{2\pi r}{\lambda}- ct)$ $\lambda = 4.9~ft$ $c = 1026~ft/s$ $a = 0.4~lb/ft^2$ $r = 10~ft$ $P = \frac{0.4}{10}~cos[\frac{(2\pi) (10)}{4.9}- 1026~t]$ We can see a sketch of the graph in the window $[0,0.05]$ by $[-0.05, 0.05]$ The sound pressure $P$ at a distance of ten feet from the source oscillates continuously between $0.04$ and $-0.04$

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