Chapter 12: Problem 6
give a geometric description of the set of points in space whose coordinates satisfy the given pairs of equations \(x^{2}+y^{2}=4, \quad z=-2\)
Short Answer
Expert verified
A circle of radius 2 in the plane z = -2, centered at (0, 0, -2).
Step by step solution
01
Understand Each Equation
The first equation is \( x^2 + y^2 = 4 \). This represents a circle in the xy-plane with a radius of 2, centered at the origin (0,0).The second equation is \( z = -2 \). This represents a plane parallel to the xy-plane, located at z = -2.
02
Combine the Equations
To find the geometric description, combine both equations. The circle \( x^2 + y^2 = 4 \) lies in a specific plane given by \( z = -2 \). Therefore, every point \( (x, y, z) \) that satisfies both equations lies on this circle in the plane \( z = -2 \).
03
Describe the Geometry
The intersection of the circle and the plane results in a circular path. Therefore, the set of points that satisfy both equations form a circle of radius 2 centered at \( (0, 0, -2) \) in the three-dimensional coordinate space.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Coordinates
Coordinates are numerical values representing a point's position in space. They provide a unique identifier for any location in a given space. In three-dimensional space, we use three numbers, typically denoted as \((x, y, z)\), as coordinates.
- The first number, \(x\), indicates the position along the x-axis, which typically runs horizontally.
- The second number, \(y\), specifies the position along the y-axis, usually running vertically.
- The third number, \(z\), represents the height or depth, indicating the position along the z-axis.
Exploring Three-dimensional Space
Three-dimensional (3D) space extends in three directions, typically marked by x, y, and z axes. This space can be visualized as a box, with each point within it having three coordinates. The concept of dimensionality is key:
- A point has no dimension, only location.
- A line or curve is one-dimensional, extending along one axis.
- A plane is two-dimensional, having length and width but no height.
- Three-dimensional space combines all these: length, width, and height.
The Concept of a Circle in Geometry
A circle is a fundamental geometric shape consisting of all points in a plane that are a fixed distance (the radius) from a center point. It is a two-dimensional shape when considered by itself, but it can be placed in a three-dimensional context. Key properties of a circle include:
- The center, denoted here as \((0, 0)\) in the xy-plane.
- The radius, the constant distance from the center to any point on the circle. In the exercise, this is 2 units.
- The circumference, the total distance around the circle.
Understanding Planes in Three-dimensional Space
Planes are flat, two-dimensional surfaces extending infinitely within their dimensions. In three-dimensional space, a plane can be imagined as a sheet of paper extending without end.
- A plane can be defined by a point and a normal (perpendicular) vector, or by an equation involving coordinates.
- In our case, the equation \(z = -2\) describes a plane parallel to the xy-plane but shifted down by 2 units along the z-axis.
- This plane holds all points in space where the z-coordinate is constantly -2.