Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 7 - Section 7.2 - Addition and Subtraction Formulas - 7.2 Exercises - Page 552: 64

Answer

$\sqrt 3 \sin 2x+ \cos 2x=2 \sin 2 (x+\dfrac{\pi}{12})$ It has maximum value =2 and phase shift $=\dfrac{\pi}{12}$

Work Step by Step

Here, we have $\sqrt 3 \sin 2x+ \cos 2x=R \sin (2x-\phi)$ Since, the angle $\phi$ lies in the fourth quadrant so, $\phi=-\dfrac{\pi}{6}$ Thus, $\cos \phi=\cos \dfrac{\pi}{6}=\dfrac{\sqrt 3}{2}$; $\sin \phi=\sin \dfrac{\pi}{6}=\dfrac{-1}{2}$ Thus, $R^2(\cos^2 \phi+\sin^2 \phi)=(\sqrt 3)^2+(-1)^2$ This gives: $R=2$ since, the trigonometric function has period of $2 \pi$, so we will have to add $2 \pi$ $\sqrt 3 \sin 2x+ \cos 2x=R \sin (2x-\phi)$ Thus, we have $\sqrt 3 \sin 2x+ \cos 2x=2 \sin 2 (x+\dfrac{\pi}{12})$ It has maximum value =2 and phase shift $=\dfrac{\pi}{12}$
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