Chapter 11: Problem 10
Name and sketch the graph of each of the following equations in three-space. $$ -x^{2}+y^{2}+z^{2}=0 $$
Short Answer
Expert verified
The graph is a double cone symmetrical about the x-axis.
Step by step solution
01
Identify the Equation Type
The given equation is \[-x^2 + y^2 + z^2 = 0\]. This equation is of the form \[-x^2 + y^2 + z^2 = 0\]. This resembles the equation of a cone in three-dimensional space, where \(x^2 = y^2 + z^2\).
02
Rewrite the Equation
Rearrange the equation to isolate \(x^2\) on one side:\[x^2 = y^2 + z^2\].This confirms that the surface is a double cone with its vertex at the origin, opening in the positive and negative x-directions.
03
Analyze the Shape
The equation \(x^2 = y^2 + z^2\) represents a double cone. If we slice the graph with a plane containing the x-axis (i.e., the yz-plane), the sections will be a pair of lines crossing at the origin. If we fix x to any positive or negative constant, the resulting equation is a circle.
04
Sketch the Graph
Begin by sketching the yz-plane with the cone opening symmetrically around the x-axis, since the cone extends indefinitely on both sides of the origin along the x-axis. The intersection with any plane parallel to the yz-plane results in a circle, reflecting the equation \(x^2 = y^2 + z^2\).
05
Verify by Cross Sections
For constant values of \(x\), say \(x = c\), the equation becomes \[c^2 = y^2 + z^2\].This is a circle in the yz-plane with center at the origin and radius \(c\). This confirms the graph is a cone with circular cross-sections.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Double Cone
A double cone is a fascinating three-dimensional shape. Imagine two ice cream cones connected at their tips, sharing the same axis.
- Each cone extends infinitely in opposite directions from the vertex.
- It is symmetrical around the axis that passes through its vertex.
- A plane intersecting the cone through its vertex produces two lines.
Three-Dimensional Space
Three-dimensional space is the environment where these equations come to life. It's often referred to as 3D space and can be visualized as a vast grid.
- It includes three axes: x, y, and z, each representing a different dimension.
- Objects like cones can have depth, width, and height in this space.
- When graphing, it's important to understand the coordination between these three axes.
Equation of a Cone
The equation of a cone is essential for understanding its geometry.
- A standard cone equation can be written as \[x^2 = y^2 + z^2\].
- This represents a perfect cone with its axis along the x-line.
- The vertex is typically placed at the origin, allowing symmetric extension.
Cartesian Coordinates
Cartesian coordinates are the backbone for 3D graphing. They help us place every point in space accurately.
- Defined by three values (x, y, and z) for three-dimensional space.
- These coordinates help in visualizing the position and relation of points and shapes.
- Equations convert easily to visual representations when plotted on Cartesian axes.