Chapter 15: Problem 3
In Exercises \(1-12,\) sketch the graph described by the following cylindrical coordinates in three-dimensional space. $$ z=-1 $$
Short Answer
Expert verified
The graph is a horizontal plane located at \(z = -1\) in 3D space.
Step by step solution
01
Understand the Cylindrical Coordinate System
In the cylindrical coordinate system, a point in space is described by the coordinates \(r, \theta, z\). Here, \(r\) is the radius (distance from the origin in the xy-plane), \(\theta\) is the angle from the positive x-axis in the xy-plane, and \(z\) is the height above the xy-plane.
02
Interpret the Equation
The given equation is \(z = -1\). This implies that for any point on or described by this equation, the z-coordinate is a constant value of -1. The coordinates \(r\) and \(\theta\) are not specified, which means they can take any value.
03
Visualize the Graph in 3D Space
Since \(z = -1\) and \(r\) and \(\theta\) can be any value, all the points that are one unit below the xy-plane form a horizontal plane parallel to the xy-plane itself. This plane is located at \(z = -1\).
04
Sketch the Graph
To sketch the graph, imagine or draw a 3-dimensional coordinate system. Draw a plane that is horizontal and passes through the point where \(z = -1\) in the z-axis. This plane extends infinitely in the x and y directions. It's parallel to the xy-plane and located one unit below it.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
3-dimensional space
Three-dimensional space is the environment where we visualize and analyze 3D objects. It extends the two-dimensional concept of a plane by adding an additional z-axis, allowing us to model the real world more accurately. In 3D space, every point is represented using three coordinates, typically labeled as
- **x** - The position left or right across the horizontal plane
- **y** - The position up or down along the vertical plane
- **z** - The depth or height above or below the xy-plane
graph sketching
Graph sketching in cylindrical coordinates involves translating the abstract mathematical information into a visual representation. For the given exercise, with the equation \(z = -1\), the task is to sketch a plane in 3D space:
- Identify the role of each coordinate: Here, only the z-coordinate is specified, meaning the height is constant across all x and y values
- Visualize how this constant z value impacts the graph: This results in a flat plane extending infinitely in both the x and y directions
- Finally, represent this visually either by drawing or imagining a plane parallel to the xy-plane, but at a set distance below it
cylindrical coordinate system
The cylindrical coordinate system is a three-dimensional counterpart to the two-dimensional polar coordinate system. It uses three dimensions:
- **r** - The radial distance from the origin, showing how far the point is from the vertical z-axis
- **\(\theta\)** - The angular coordinate, often measured in radians, indicating the direction of the point from the positive x-axis
- **z** - The typical height or vertical displacement from the xy-plane
horizontal plane in 3D
A horizontal plane in three-dimensional space is a flat, two-dimensional surface that runs parallel to the xy-plane. In the context of the exercise, the equation \(z = -1\) describes such a plane.
- This specific horizontal plane is one unit below the xy-plane along the z-axis
- It extends infinitely in the directions of the x and y axes, forming a sheet-like surface that does not curve or slope
- The importance of recognizing this plane helps in understanding spatial relationships and positioning in 3D space