Chapter 10: Problem 31
Find an equation for the surface consisting of all points that are equidistant from the point \((-1,0,0)\) and the plane \(x=1 .\) Identify the surface.
Short Answer
Expert verified
The surface is a paraboloid with the equation \(y^2 + z^2 = -4x\), opening along the negative x-axis.
Step by step solution
01
Define the Distance to a Point
The distance from a point \((x, y, z)\) to the point \((-1, 0, 0)\) can be calculated using the distance formula. It is given by:\[\sqrt{(x + 1)^2 + y^2 + z^2}\]
02
Define the Distance to a Plane
The distance from a point \((x, y, z)\) to the plane defined by \(x = 1\) is the absolute value of the difference between the x-coordinate, \(x\), and 1. Thus, the distance is given by:\[|x - 1|\]
03
Set Distances Equal
A point is equidistant from \((-1, 0, 0)\) and the plane \(x=1\) if its distance to each is equal. Therefore, we set the distances calculated in Steps 1 and 2 equal to each other:\[\sqrt{(x + 1)^2 + y^2 + z^2} = |x - 1|\]
04
Square Both Sides
To eliminate the square root, square both sides of the equation from Step 3:\[(x + 1)^2 + y^2 + z^2 = (x - 1)^2\]
05
Expand and Simplify
Expand the squared terms:\[(x^2 + 2x + 1) + y^2 + z^2 = x^2 - 2x + 1\]Simplify by subtracting \(x^2 + 1\) from both sides:\[2x + y^2 + z^2 = -2x\]
06
Solve for y and z Terms
Move the \(2x\) term to the other side:\[y^2 + z^2 = -4x\]Divide by \(-1\) to rearrange the equation in a standard form:\[y^2 + z^2 = -4x\]
07
Identify the Surface
The equation obtained resembles that of a paraboloid, which is defined as being symmetric around an axis (here the x-axis) and extends infinitely in one direction. The form \(y^2 + z^2 = -4x\) shows it to be a paraboloid opening along the negative x-axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Distance to a Point
In mathematics, the distance from one point to another is a measure of how far apart the two points are. The distance from a point \((x, y, z)\) to a fixed point, such as \((-1,0,0)\), can be calculated using the three-dimensional distance formula. This formula is given as:\[ \sqrt{(x + 1)^2 + y^2 + z^2} \]This formula comes from the Pythagorean theorem, extended into three dimensions. It calculates the straight-line (or "Euclidean") distance between two points in space. Here, you add 1 to the x-coordinate because the fixed point has an x-value of -1. Every part of this formula represents component-wise differences raised to power of two. This ensures that the distance measure remains positive, regardless of the position of the points in the three-dimensional space.
Distance to a Plane
The concept of distance to a plane involves finding how far a point is from a given plane. Here, our plane is described simply by the equation \(x = 1\). Planes in three-dimensional space often involve a more complex relationship between x, y, and z coordinates, but this one is straightforward.For a point \((x, y, z)\) in space, the distance to the plane \(x = 1\) is the absolute value of the x-coordinate minus 1, which is represented by:\[ |x - 1| \]This equation reflects the direct manner in which vertical (or horizontal) distances between a point and the plane are calculated. Here, since \(x = 1\) represents a vertical plane perpendicular to the x-axis, the distance is purely determined by differences in the x-coordinate. No y or z components are required because the plane is independent of these dimensions.
Paraboloid
A paraboloid is a three-dimensional surface that looks somewhat like an infinite bowl shape. Its cross-section is a parabola, which gives it its name. In this exercise, we obtained the equation \(y^2 + z^2 = -4x\) after manipulating the distances.The equation here shows a paraboloid symmetric about the x-axis. This is because both \(y^2\) and \(z^2\) are involved, showing no preference in their dimension relative to one another.This specific equation represents a paraboloid opening along the negative x-axis, because the x-term is linear and has negative multiplication with constant.Key characteristics of paraboloids include:
- They have a vertex where they are most "narrow" or "closed." For our paraboloid, it is at the origin (0,0,0).
- When elongated infinitely in the positive or negative direction along its axis (in this case, the x-axis), it forms an open-ended surface.
- Each cross-section parallel to its base (in this case, perpendicular to the y-z plane) forms a circle.