Chapter 11: Problem 11
Convert from spherical to cylindrical coordinates. (a) \((5, \pi / 4,2 \pi / 3)\) (b) \((1,7 \pi / 6, \pi)\) (c) \((3,0,0)\) (d) \((4, \pi / 6, \pi / 2)\)
Short Answer
Expert verified
(a) \((5\sqrt{3}/2, \pi/4, -5/2)\), (b) \((0, 7\pi/6, -1)\), (c) \((0, 0, 3)\), (d) \((4, \pi/6, 0)\)."
Step by step solution
01
Understand the Coordinate Conversion Formulas
To convert from spherical to cylindrical coordinates, we use the following formulas: - For cylindrical coordinates \(r, \theta, z\), the corresponding spherical coordinates \(\rho, \phi, \theta\) are related as follows: 1. \(r = \rho \sin \phi\)2. \(\theta = \theta\) (same in both systems)3. \(z = \rho \cos \phi\)
02
Convert (a) \\( (5, \pi / 4, 2\pi / 3) \\\)
First, identify the spherical coordinates \(\rho = 5, \phi = 2\pi / 3, \theta = \pi / 4\).1. Compute \(r = \rho \sin \phi = 5 \sin(2\pi / 3) = 5(\sqrt{3}/2) = 5\sqrt{3}/2\).2. \(\theta = \pi / 4\) remains the same.3. Compute \(z = \rho \cos \phi = 5 \cos(2\pi / 3) = 5(-1/2) = -5/2\).Hence, the cylindrical coordinates are \((5\sqrt{3}/2, \pi / 4, -5/2)\).
03
Convert (b) \\( (1, 7\pi / 6, \pi) \\\)
First, identify the spherical coordinates \(\rho = 1, \phi = \pi, \theta = 7\pi / 6\).1. Compute \(r = \rho \sin \phi = 1 \sin(\pi) = 0\).2. \(\theta = 7\pi / 6\) remains the same.3. Compute \(z = \rho \cos \phi = 1 \cos(\pi) = -1\).Hence, the cylindrical coordinates are \( (0, 7\pi/6, -1) \).
04
Convert (c) \\( (3, 0, 0) \\\)
First, identify the spherical coordinates \(\rho = 3, \phi = 0, \theta = 0\).1. Compute \(r = \rho \sin \phi = 3 \sin(0) = 0\).2. \(\theta = 0\) remains the same.3. Compute \(z = \rho \cos \phi = 3 \cos(0) = 3\).Hence, the cylindrical coordinates are \((0, 0, 3)\).
05
Convert (d) \\( (4, \pi / 6, \pi / 2) \\\)
First, identify the spherical coordinates \(\rho = 4, \phi = \pi/2, \theta = \pi/6\).1. Compute \(r = \rho \sin \phi = 4 \sin(\pi/2) = 4(1) = 4\).2. \(\theta = \pi/6\) remains the same.3. Compute \(z = \rho \cos \phi = 4 \cos(\pi/2) = 4(0) = 0\).Hence, the cylindrical coordinates are \( (4, \pi/6, 0) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Spherical Coordinates
Spherical coordinates are a way to represent points in three-dimensional space using three values: \( (\rho, \phi, \theta) \). Each of these components has a specific geometric meaning, making this system particularly useful in fields like physics and engineering.
Here is what each term represents:
Here is what each term represents:
- \( \rho \) (rho) is the radial distance from the origin to the point.
- \( \phi \) (phi) is the polar angle, measured from the positive z-axis downward.
- \( \theta \) (theta) is the azimuthal angle in the xy-plane, measured from the positive x-axis.
Cylindrical Coordinates
Cylindrical coordinates provide another way to describe positions in three-dimensional space using \((r, \theta, z)\), blending elements of polar and Cartesian coordinates.
Here's how each parameter is defined:
Here's how each parameter is defined:
- \( r \) is the radial distance from the z-axis to the point's projection in the xy-plane.
- \( \theta \) (theta) is the angle that the radial line makes with the positive x-axis, similar to the angle in polar coordinates.
- \( z \) represents the height above or below the xy-plane, just like in Cartesian coordinates.
- Compute \( r \) using \( r = \rho \sin \phi \).
- Maintain \( \theta \) as it remains the same.
- Calculate \( z \) with \( z = \rho \cos \phi \).
Trigonometric Functions
Trigonometric functions are mathematical functions that relate angles to side ratios in right-angled triangles. They are crucial in converting coordinates because they offer a natural way to deal with angles and periodic patterns.
The two main functions used in coordinate conversions are:
The two main functions used in coordinate conversions are:
- Sine \( \sin \phi \): Determines the component of the radius that lies in the xy-plane. It's used in finding the radial distance \( r \) when converting from spherical to cylindrical coordinates.
- Cosine \( \cos \phi \): Provides the height component by dictating how much of the radius aligns with the z-axis. In conversions, it determines \( z \).