Chapter 12: Problem 45
In Problems 45 through 52 . describe and sketch the surface or solid described by the given equations and/or inequalities. \(r=3,-1 \leqq z \leqq 1\)
Short Answer
Expert verified
This describes a finite cylinder with radius 3 and height extending from \( z = -1 \) to \( z = 1 \).
Step by step solution
01
Identify the Surface
The given equation is in cylindrical coordinates, where \( r = 3 \) describes a cylindrical surface centered on the z-axis with a radius of 3. The equation is not dependent on \( \theta \), indicating it extends around the entire circle of radius 3.
02
Apply the Inequality
The inequality \(-1 \leq z \leq 1\) restricts the height of the cylinder along the \( z \)-axis. This means the cylinder extends from \( z = -1 \) to \( z = 1 \).
03
Sketch the Surface
To sketch the described solid, draw a cylinder centered at the origin (0,0) in the \( xy \)-plane with a radius of 3. The vertical extent of the cylinder runs between the \( z \)-planes at \( z = -1 \) and \( z = 1 \). This creates a finite-height cylindrical surface.
04
Describe the Solid
The surface is a finite cylinder with base circles in the \( xy \)-plane having radius 3 and the top and bottom base at \( z = 1 \) and \( z = -1 \), respectively.
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Cylinder
A cylinder is a three-dimensional surface formed by translating a closed curve, most commonly a circle, along an axis. In this context, the axis is the z-axis. The cylinder described here is formed by revolving a circle of radius 3 around the z-axis, extending indefinitely if not for the limits set by the height.
- Has a circular base, typically defined in the xy-plane.
- Extends along the z-axis; can be infinite or restricted to a specific range.
- In cylindrical coordinates, it's often described by fixing the radius, here given by \( r = 3 \).
Radius
The radius in any context is the distance from the center of a circle to its outer edge. In this problem, the radius is crucial as it clearly defines how wide the cylindrical surface is from the axis.
- Here, the radius is fixed at 3, meaning every point on the surface is exactly 3 units away from the z-axis.
- This radius dictates the circular size of the base in the xy-plane.
- A consistent radius maintains the cylinder's uniform width.
Inequality
Inequalities in this context help us define and limit the regions in space where the cylinder is present. The inequality \(-1 \leq z \leq 1\) defines the height of the cylinder.
- Dictates the boundary of the cylinder along the z-axis.
- Z extends from -1 to 1, creating a finite height rather than an infinite extension.
- Allows us to think of the cylinder as having a top and bottom at these z-values.
Cylindrical Surface
A cylindrical surface is a three-dimensional structure made by revolving a line around an axis, not intersecting it. Here, we see a cylindrical surface with a determined radius and height.
- The equation \( r = 3 \) characterizes the cylindrical surface around a central axis.
- Not dependent on \( \theta \), it suggests a seamless, rounded surface.
- The surface is capped between \( z = -1 \) and \( z = 1 \).