Chapter 2: Problem 408
For the following exercises, the spherical coordinates of a point are given. Find its associated cylindrical coordinates. \(\left(4, \frac{\pi}{4}, \frac{\pi}{6}\right)\)
Short Answer
Expert verified
Cylindrical coordinates: \((2, \frac{\pi}{4}, 2\sqrt{3})\).
Step by step solution
01
Understand the Problem
We need to convert the spherical coordinates \((4, \frac{\pi}{4}, \frac{\pi}{6})\) into cylindrical coordinates. In spherical coordinates, \(4\) is the radial distance \(\rho\), \(\frac{\pi}{4}\) is the azimuthal angle \(\theta\), and \(\frac{\pi}{6}\) is the polar angle \(\phi\). For cylindrical coordinates, we need to find \((r, \theta, z)\).
02
Calculate the Radial Distance r
In cylindrical coordinates, the radial distance \(r\) is given by \(r = \rho \sin \phi\). Substitute the values: \(\rho = 4\) and \(\phi = \frac{\pi}{6}\). \[ r = 4 \sin \left(\frac{\pi}{6}\right) = 4 \times \frac{1}{2} = 2 \]
03
Determine the Azimuthal Angle θ
The azimuthal angle \(\theta\) in cylindrical coordinates is the same as the azimuthal angle in spherical coordinates. Therefore, \(\theta = \frac{\pi}{4}\).
04
Find the z-coordinate
The \(z\)-coordinate in cylindrical coordinates is obtained using \(z = \rho \cos \phi\). Substitute the values: \(\rho = 4\) and \(\phi = \frac{\pi}{6}\). \[ z = 4 \cos \left(\frac{\pi}{6}\right) = 4 \times \frac{\sqrt{3}}{2} = 2\sqrt{3} \]
05
Write the Cylindrical Coordinates
Combine the calculated values to write the cylindrical coordinates: \( (r, \theta, z) = (2, \frac{\pi}{4}, 2\sqrt{3}) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Cylindrical Coordinates
Cylindrical coordinates are a three-dimensional coordinate system that extends polar coordinates by adding a height element. They're called cylindrical because they naturally describe shapes like cylinders. This system is useful for problems involving symmetry around an axis.
- Components: Cylindrical coordinates consist of three elements \(r, \theta, z\)\;, where \(r\) is the radial distance from the origin in the xy-plane, \(\theta\) is the angular displacement from a reference direction, and \(z\) is the height above the xy-plane.
- Applications: It's particularly useful in engineering and physics for modeling problems where one of the axes is rotationally symmetric, like the flow of fluids in a pipe.
Spherical Coordinates
Spherical coordinates offer a powerful way to describe locations in a three-dimensional space, particularly for points on spheres. It's like a globe's latitude and longitude but includes the radius too.
- Components: These coordinates are determined by \(\rho, \theta, \phi\)\; where \(\rho\) is the distance from the origin to the point, \(\theta\) is the angle in the xy-plane from the positive x-axis, and \(\phi\) is the angle from the positive z-axis to the point.
- Conversions: Given their nature, spherical coordinates convert naturally to both Cartesian and cylindrical systems through trigonometric relationships, helping solve spatial problems.
- Usage: They are immensely helpful in physics, particularly in scenarios involving waves and fields where symmetry around a point makes the math simpler.
Trigonometric Functions
Trigonometric functions, like sine and cosine, play a key role in converting between coordinate systems by defining relationships between angles and distances. In coordinate conversion, they're like bridge-builders.
- Sine Function: Used to determine the radial distance \(r\) in cylindrical coordinates from spherical inputs, via the formula \(r = \rho \sin \phi\).
- Cosine Function: Vital for finding the z-coordinate through \(z = \rho \cos \phi\).
- Angles and Distances: Trigonometric functions relate angles to linear dimensions, which is essential for translating between different coordinate systems.
Mathematical Problem Solving
Mathematical problem-solving prowess is key when transitioning between different coordinate systems. It involves analysis, strategy, and computation.
- Understanding the Problem: The initial step in any conversion is recognizing each element of the coordinate systems involved—knowing what needs mapping to what.
- Strategic Calculations: Carefully apply the appropriate trigonometric formulas to translate between systems, ensuring each step logically follows the previous.
- Verification: Always check the final calculations to ensure accuracy—small errors in trigonometric computation can lead to significant deviations.