Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 6 - Section 6.3 - Trigonometric Functions of Angles - 6.3 Exercises - Page 499: 63

Answer

$2.46$

Work Step by Step

The area $A$ of a sector with central angle of $\theta$ radians is $ A_{s}=\displaystyle \frac{1}{2}r^{2}\theta$. The area of a triangle with sides of lengths $a$ and $b$ and with included angle $\theta$ is $A_{t}=\displaystyle \frac{1}{2} ab \sin\theta$ To convert degrees to radians, multiply by $\pi/180$. ------ The shaded area is obtained by subtracting the triangle area from the sector area. $A=A_{s}-A_{t}$ $A=\displaystyle \frac{1}{2}\cdot 2^{2}\cdot\frac{120\pi}{180} - \frac{1}{2} 2\cdot 2\cdot\sin 120^{o}$ The reference angle for $120^{o}$, (q.II, sine is positive) is $60^{o}$, and $\displaystyle \sin 120^{o}=\sin 60^{o}=\frac{\sqrt{3}}{2}$ $ A= \displaystyle \frac{4\pi}{3}-\sqrt{3}\approx$2.45673939722$\approx 2.46$
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