Chapter 1: Problem 16
Find the distance between point \(P=(3,1,2)\) and the plane given by \(x-2 y+z=5\) (see the following figure).
Short Answer
Expert verified
The distance is \(\frac{\sqrt{6}}{3}\).
Step by step solution
01
Define the Distance Formula
The distance, \(d\), from a point \((x_1, y_1, z_1)\) to a plane given by \(ax + by + cz + d = 0\) is calculated using the formula:\[ d = \frac{|ax_1 + by_1 + cz_1 + d|}{\sqrt{a^2 + b^2 + c^2}} \]Where \(a\), \(b\), and \(c\) are the coefficients of \(x\), \(y\), and \(z\) in the plane equation.
02
Identify Coefficients and Substitutions
For the given plane equation \(x - 2y + z = 5\), rewrite it in the form \(ax + by + cz + d = 0\):\[ x - 2y + z - 5 = 0 \]From this, we identify \(a = 1\), \(b = -2\), \(c = 1\), and \(d = -5\). The point \(P = (3, 1, 2)\) will be \((x_1, y_1, z_1) = (3, 1, 2)\).
03
Calculate Numerator of the Formula
Substitute the point \(P = (3, 1, 2)\) into the plane equation:\[ 1(3) + (-2)(1) + 1(2) - 5 \]This simplifies to:\[ 3 - 2 + 2 - 5 = -2 \]The absolute value is: \[ |-2| = 2 \]
04
Compute Denominator of the Formula
Using the coefficients \(a = 1\), \(b = -2\), and \(c = 1\), compute the magnitude of the normal vector:\[ \sqrt{1^2 + (-2)^2 + 1^2} = \sqrt{1 + 4 + 1} = \sqrt{6} \]
05
Calculate the Distance
Plug the results from the numerator and denominator into the distance formula:\[ d = \frac{2}{\sqrt{6}} \]Simplify the expression:\[ d = \frac{2\sqrt{6}}{6} = \frac{\sqrt{6}}{3} \]
06
Final Result
The distance from point \(P = (3,1,2)\) to the plane \(x-2y+z=5\) is \(\frac{\sqrt{6}}{3}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Distance Formula
The distance formula is a crucial mathematical tool for finding the shortest distance between a point and a plane. The idea behind this formula is to measure how far you need to travel in a perpendicular direction from a given point to the nearest point on the plane.
To calculate this distance, you can use the formula: \[ d = \frac{|ax_1 + by_1 + cz_1 + d|}{\sqrt{a^2 + b^2 + c^2}} \] Here’s what each symbol represents:
To calculate this distance, you can use the formula: \[ d = \frac{|ax_1 + by_1 + cz_1 + d|}{\sqrt{a^2 + b^2 + c^2}} \] Here’s what each symbol represents:
- \( a \), \( b \), and \( c \): the coefficients of the variables \( x \), \( y \), and \( z \), respectively, in the plane equation.
- \( x_1 \), \( y_1 \), and \( z_1 \): the coordinates of the point from which you’re measuring the distance.
- \( d \): the constant in the plane equation when written in the form \( ax + by + cz + d = 0 \).
- \(|...|\): absolute value, ensuring the distance is always non-negative.
- \(\sqrt{...}\): square root calculates the magnitude of the normal vector to the plane.
Plane Equation Coefficients
The coefficients in the equation of a plane play a vital role in determining the characteristics of the plane. When you see an equation like \( x - 2y + z = 5 \), these coefficients of \( x \), \( y \), and \( z \) (\( 1 \), \(-2\), and \( 1 \), respectively) are front and center.
These coefficients \((a, b, c)\) help identify the plane’s orientation in space. The plane can be rewritten as \( ax + by + cz - d = 0 \), where \( a = 1\), \( b = -2\), \( c = 1\), and \( d = -5\).
Recognizing and manipulating these coefficients is essential in:
These coefficients \((a, b, c)\) help identify the plane’s orientation in space. The plane can be rewritten as \( ax + by + cz - d = 0 \), where \( a = 1\), \( b = -2\), \( c = 1\), and \( d = -5\).
Recognizing and manipulating these coefficients is essential in:
- Translating the plane equation into the standard form necessary for calculations.
- Understanding how changes in \( a \), \( b \), and \( c \) affect the slope and tilt of the plane in three-dimensional space.
- Substituting them directly in the distance formula to estimate the shortest distance from a point to the plane.
Normal Vector Magnitude
In the geometry of planes, the normal vector is key for understanding how the plane is oriented in space. The normal vector is a perpendicular vector to the plane and is defined by the coefficients \(a\), \(b\), and \(c\) from the plane equation \(ax + by + cz + d = 0\).
To find its magnitude, and hence understand the scaling factor for the vector, use: \[ \sqrt{a^2 + b^2 + c^2} \] This converts the vector into a single number, measuring its length.
Let’s break it down:
To find its magnitude, and hence understand the scaling factor for the vector, use: \[ \sqrt{a^2 + b^2 + c^2} \] This converts the vector into a single number, measuring its length.
Let’s break it down:
- In the example equation \( x - 2y + z = 5 \), the coefficients \((1, -2, 1)\) describe the direction in which the normal vector points.
- The magnitude \( \sqrt{1^2 + (-2)^2 + 1^2} = \sqrt{6} \) gives the length of the vector.
- This magnitude is crucial in the distance formula because it scales the numerator to normalize the actual distance calculation.