Calculus (3rd Edition)

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

Chapter 13 - Vector Geometry - 13.2 Vectors in Three Dimensions - Exercises - Page 660: 53

Answer

The two lines intersect. Intersection point: $\left( {3,4,7} \right)$.

Work Step by Step

Suppose the lines intersect and there is point of intersection at $t$ and $s$ such that ${{\bf{r}}_1}\left( t \right) = {{\bf{r}}_2}\left( s \right)$. So, $\left( {0,1,1} \right) + t\left( {1,1,2} \right) = \left( {2,0,3} \right) + s\left( {1,4,4} \right)$ In component forms, we have $x = t = 2 + s$, ${\ \ }$ $y = 1 + t = 4s$, ${\ \ }$ $z = 1 + 2t = 3 + 4s$ Solving the first two equations, we get $t=3$ and $s=1$. These values satisfies the third equation. Therefore, there exists point of intersection. Substituting $t=3$ in ${{\bf{r}}_1}\left( t \right) = \left( {0,1,1} \right) + t\left( {1,1,2} \right)$ gives the intersection point: ${{\bf{r}}_1}\left( 3 \right) = \left( {3,4,7} \right)$. Likewise, substituting $s=1$ in ${{\bf{r}}_2}\left( s \right) = \left( {2,0,3} \right) + s\left( {1,4,4} \right)$ also gives the same intersection point: ${{\bf{r}}_2}\left( 1 \right) = \left( {3,4,7} \right)$.
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