Chapter 16: Problem 3
Find an equation for the surface. The top half of the sphere \(x^{2}+y^{2}+z^{2}=1\) in cylindrical coordinates.
Short Answer
Expert verified
The equation is \(r^{2} + z^{2} = 1\) with \(z \geq 0\).
Step by step solution
01
Identify the Original Equation
The equation given is for a sphere: \(x^{2} + y^{2} + z^{2} = 1\). This equation describes a sphere with radius 1 centered at the origin.
02
Convert to Cylindrical Coordinates
In cylindrical coordinates, the relations are \(x = r \cos \theta\), \(y = r \sin \theta\), and \(z = z\). We substitute these into the sphere equation: \( (r \cos \theta)^{2} + (r \sin \theta)^{2} + z^{2} = 1\).
03
Simplify the Equation
Simplify the equation: \((r \cos \theta)^{2} + (r \sin \theta)^{2} = r^{2}\). Hence, the equation becomes \(r^{2} + z^{2} = 1\).
04
Consider the Top Half Sphere
For the top half of the sphere, we need \(z\) to be non-negative. Therefore, the condition is \(z \geq 0\).
05
Final Equation in Cylindrical Coordinates
The equation of the top half of the sphere in cylindrical coordinates is \(r^{2} + z^{2} = 1\) with \(z \geq 0\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Sphere Equation
A sphere in three-dimensional space can be described using the sphere equation. This equation generally takes the form
- \[ x^2 + y^2 + z^2 = r^2 \]
- where \( r \) represents the radius of the sphere.
- The coordinates \( (x, y, z) \) represent any point on the surface of this sphere.
- \[ x^2 + y^2 + z^2 = 1 \]
Coordinate Transformation
Coordinate transformation refers to changing a set of coordinates from one system to another. The primary goal is to simplify equations or make analyses more convenient
- for the problem at hand.
- \( (x, y, z) \)
- to cylindrical coordinates
- \( (r, \theta, z) \),
- \( x = r \cos \theta \),
- \( y = r \sin \theta \),
- \( z = z \).
Surface Equation
When we talk about the surface equation of a geometric shape, we mean the equation that precisely describes all the points that belong to the surface of that shape. In this exercise,
- we initially deal with the sphere's equation
- and then transform it into a cylindrical form.
- \[ x^2 + y^2 + z^2 = 1 \],
- \[ r^2 + z^2 = 1 \].
Multivariable Calculus
Multivariable calculus deals with functions of more than one variable. It extends the principles of calculus to higher dimensions. When studying shapes in three-dimensional space,
- it's crucial to understand how these variables interact.
- different surfaces,
- their properties, and
- how they can be represented in varied coordinate systems, like cylindrical.
- offering tools to manipulate and redefine equations to suit our analyses.