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: 32

Answer

See proof

Work Step by Step

\begin{align*} \ell_1: \quad & x_1 = 2+8t_1, \quad y_1=6-8t_1, \quad z_1=10t_1 \\ \ell_2: \quad & x_2 = 3+8t_2, \quad y_2=5-3t_2, \quad z_2=6+t_2 \ \end{align*} To check if the lines are skew, we can see if there exists a common value for $t_1$ and $t_2$ such that the lines intersect. We can equate the respective parametric equations of the two lines and solve for $t_1$ and $t_2$: \begin{align*} x_1 = x_2 \quad & \Rightarrow \quad 2+8t_1 = 3+8t_2 \\ y_1 = y_2 \quad & \Rightarrow \quad 6-8t_1 = 5-3t_2 \\ z_1 = z_2 \quad & \Rightarrow \quad 10t_1 = 6+t_2 \end{align*} Solving this system of equations yields $t_1 = 1$, $t_2 = -1$, and $z_1 = 10$ (which satisfies the third equation). Since the lines do not intersect, we can conclude that they are skew. The direction vectors of the two lines are $\mathbf{v_1} = \langle 8, -8, 10 \rangle$ and $\mathbf{v_2} = \langle 8, -3, 1 \rangle$, which are not parallel. Therefore, the two lines are non-coplanar and skew.
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