Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

Chapter 7 - Test - Page 416: 27

Answer

$98.6^\circ$.

Work Step by Step

From what we learned: $\cos\theta=\frac{U\cdot V}{|U||V|}=\frac{5\cdot(-4)+12\cdot1}{\sqrt{5^2+12^2}\sqrt{(-4)^2+1^2}}=\frac{-8}{\sqrt{169}\cdot\sqrt{17}}=\frac{-8}{13\sqrt{17}}$ Thus $\theta=\cos^{-1}\frac{-8}{13\sqrt{17}}\approx98.6^\circ$.
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