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 - 11.6 Planes in 3-Space - Exercises Set 11.6 - Page 819: 10

Answer

$y-z=0$

Work Step by Step

The equation of the plane passing through the points $O(0,0,0), P(1,0,0)$ and $Q(0,1,1)$ is: \begin{aligned} &ax + by + cz = 0 \\ &\Rightarrow x\cdot a + y\cdot b + z\cdot c = 0 \\ &\Rightarrow (1\cdot a + 0\cdot b + 0\cdot c)\cdot x + (0\cdot a + 1\cdot b + 0\cdot c)\cdot y + (0\cdot a + 0\cdot b + 1\cdot c)\cdot z = 0 \\ &\Rightarrow (a,b,c)\cdot (x,y,z) = 0 \\ &\Rightarrow \langle a,b,c \rangle \cdot \langle x,y,z \rangle = 0 \ \end{aligned} Therefore, the normal vector to the plane is $\langle a,b,c \rangle$. To find the equation of the plane, we need to find the values of $a$, $b$, and $c$. We can use the fact that the plane passes through the points $O(0,0,0), P(1,0,0)$ and $Q(0,1,1)$ to find these values. Let $\vec{u} = \overrightarrow{OP} = \langle 1,0,0 \rangle$ and $\vec{v} = \overrightarrow{OQ} = \langle 0,1,1 \rangle$. Then, the normal vector to the plane is: \begin{aligned} \vec{n} &= \vec{u} \times \vec{v} \ &= \begin{vmatrix} \vec{i} & \vec{j} & \vec{k} \\ 1 & 0 & 0 \\ 0 & 1 & 1 \end{vmatrix} \ &= \langle 0,-1,1 \rangle \end{aligned} Since the plane passes through the origin, we can write the equation of the plane as: \begin{aligned} \langle a,b,c \rangle \cdot \langle x,y,z \rangle = 0 \ \Rightarrow \langle a,b,c \rangle \cdot \langle 0,0,0 \rangle = 0 \ \Rightarrow 0= 0 \ \end{aligned} Therefore, the constant term in the equation of the plane is $0$. Substituting the normal vector and the constant term in the equation of the plane, we get: \begin{aligned} \langle a,b,c \rangle \cdot \langle x,y,z \rangle = 0 \ \Rightarrow \langle 0,-1,1 \rangle \cdot \langle x,y,z \rangle = 0 \ \Rightarrow -y+z = 0 \ \Rightarrow y &= z \ \end{aligned} Thus, the equation of the plane passing through the points $O(0,0,0), P(1,0,0)$ and $Q(0,1,1)$ is $\boxed{y-z=0}$.
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