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 - 11.5 Parametric Equations Of Lines - Exercises Set 11.5 - Page 811: 29

Answer

\[ P(1,-1,2) \]

Work Step by Step

(a) The line in 2d space that passes through the point $P_{0}\left(x_{0}, y_{0}\right)$ and that is parallel to the non-zero vector $\mathbf{v}=\langle a, b\rangle=a \mathbf{i}+b \mathbf{j}$ has parametric equations \[ b t+y_{0}=y, \quad a t+x_{0}=x \] (b) The line in 3d space that passes through the point $P_{0}\left(x_{0}, y_{0}, z_{0}\right)$ and that is parallel to the non-zero vector $\mathbf{v}=\langle a, b, c\rangle=a \mathbf{i}+b \mathbf{j}+c \mathbf{k}$ has parametric equations: \[ c t+z_{0}=z, \quad b t+y_{0}=y, \quad at+x_{0}=x \] The vector equations of these lines can be written as: \[ \begin{aligned} &\left\langle x_{0}+a t, y_{0}+b t, z_{0}+c t\right\rangle = \langle x, y, z\rangle\\ &\left\langle x_{0}+a t, y_{0}+b t\right\rangle = \langle x, y\rangle \end{aligned} \] or \[ \begin{aligned} &\left\langle x_{0}, y_{0}, z_{0}\right\rangle+t\langle a, b, c\rangle= \langle x, y, z\rangle \\ &\left\langle x_{0}, y_{0}\right\rangle+t\langle a, b\rangle =\langle x, y\rangle \end{aligned} \] There are parametric equations for two lines in 3d space: \[ \begin{array}{ll} 2+t=x, & 2+3 t=y, \quad 3+t=z \\ 2+t=x, & 3+4 t=y \quad, \quad 4+2 t=z \end{array} \] These lines are intercepted if both pass through the point $P\left(x_{0}, y_{0}, z_{0}\right)$. If we equate our y-coordinates, we have that $2+3 t=3+4 t \Rightarrow t=2-3=-1$ For this value of the parameter ,we have that for $L_{1}:$ \[ P=P(2-1,2+3(-1), 3-1)=(1,-1,2)P \] and for $L_{2}$ \[ P=P(2-1,3+4(-1), 4+2(-1))=(1,-1,2)P \] So, both lines are intercepted at $(1,-1,2)P$
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