Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 11 - Three-Dimensional Space; Vectors - 11.2 Vectors - Exercises Set 11.2 - Page 783: 26

Answer

\[ \begin{array}{l} -\vec{w}+\vec{v}=\left\langle\frac{\sqrt{2}+\sqrt{3}}{2}, \frac{-\sqrt{2}+1}{2}\right\rangle \\ \vec{w}+\vec{v}=\left\langle\frac{-\sqrt{2}+\sqrt{3}}{2}, \frac{\sqrt{2}+1}{2}\right.\rangle \end{array} \]

Work Step by Step

Let $\vec{v}=\langle a, b\rangle$ be a vector in 2 -space. The norm of this vector and the angle with respect to the positive $x$ axis are \[ \begin{aligned} &\sqrt{b^{2}+a^{2}}=\|\vec{v}\| \\ b / a=\tan \phi & \end{aligned} \] respectively. So \[ \quad \|\vec{v}\| \sin \phi=b, \|\vec{v}\| \cos \phi=a \] and $\vec{v}$ can be written as \[ \vec{v}=\langle a, b\rangle=\|\vec{v}\|\langle\cos \phi, \sin \phi\rangle \] So: \[ \begin{array}{l} \vec{v}=\|\vec{v}\|\langle\cos (\pi / \phi), \sin (\pi / 6)\rangle=\left\langle\frac{\sqrt{3}}{2}, \frac{1}{2}\right\rangle \\ \vec{w}=\|\vec{w}\|\left\langle\cos \left(\frac{3 \pi}{4}\right), \sin \left(\frac{3 \pi}{4}\right)\right\rangle=\left\langle-\frac{\sqrt{2}}{2}, \frac{\sqrt{2}}{2}\right\rangle \end{array} \] The components of $-\vec{w}+\vec{v}$ and $\vec{w}+\vec{v}$ are \[ \begin{array}{l} \vec{w}+\vec{v}=\left\langle-\frac{\sqrt{2}}{2}, \frac{\sqrt{2}}{2}\right\rangle+\left\langle\frac{\sqrt{3}}{2}, \frac{1}{2}\right\rangle=\left\langle\frac{-\sqrt{2}+\sqrt{3}}{2}, \frac{\sqrt{2}+1}{2}\right\rangle \\ -\vec{w}+\vec{v}=-\left\langle-\frac{\sqrt{2}}{2}, \frac{\sqrt{2}}{2}\right\rangle+\left\langle\frac{\sqrt{3}}{2}, \frac{1}{2}\right\rangle=\left\langle\frac{\sqrt{2}+\sqrt{3}}{2}, \frac{-\sqrt{2}+1}{2}\right\rangle \end{array} \]
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