Trigonometry (10th Edition)

Published by Pearson
ISBN 10: 0321671775
ISBN 13: 978-0-32167-177-6

Chapter 7 - Applications of Trigonometry and Vectors - Section 7.5 Applications of Vectors - 7.5 Exercises - Page 336: 15

Answer

The ship is a distance of 13.5 miles from the port. The bearing from port is $50.4^{\circ}$

Work Step by Step

Let $a = 10.4~mi$ Let $b = 4.6~mi$ Let angle $C$ be the angle between these two vectors. Then $C = 34^{\circ}+90^{\circ} = 124^{\circ}$ We can use the law of cosines to find $c$, the distance of the ship from the port: $c = \sqrt{a^2+b^2-2ab~cos~C}$ $c = \sqrt{(10.4~mi)^2+(4.6~mi)^2-(2)(10.4~mi)(4.6~mi)~cos~124^{\circ}}$ $c = \sqrt{182.8~mi^2}$ $c = 13.5~mi$ The ship is a distance of 13.5 miles from the port. We can use the law of sines to find the angle $B$ between the resultant vector and the vector of $10.4 ~mi$: $\frac{c}{sin~C} = \frac{b}{sin~B}$ $sin~B = \frac{b~sin~C}{c}$ $B = arcsin(\frac{b~sin~C}{c})$ $B = arcsin(\frac{(4.6~mi)~sin~124^{\circ}}{13.5~mi})$ $B = arcsin(0.2825)$ $B = 16.4^{\circ}$ The bearing from port is $34^{\circ}+16.4^{\circ}$ which is $50.4^{\circ}$
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