Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 13 - Vector Geometry - 13.5 Planes in 3-Space - Exercises - Page 685: 60



Work Step by Step

By making use of the result from problem 36 (d), we get $ n_1=\langle 1,1,1\rangle $ and we have $ n_2=\langle 1,0,0\rangle $; then we get \begin{align*} \cos \theta &=\frac{n_1 \cdot n_2}{\|n_1\|\|n_2\|}\\ &=\frac{1+0+0}{\sqrt{1+1+1}\sqrt{1+0+0}}\\ &=\frac{1}{\sqrt{3} }. \end{align*} That is $$\theta=54.73^o.$$
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