Chapter 9: Problem 66
Convert the points given in rectangular coordinates to spherical coordinates. $$ \left(-\frac{\sqrt{3}}{2}, 0,-\frac{1}{2}\right) $$
Short Answer
Expert verified
Spherical coordinates are \((1, \pi, \frac{2\pi}{3})\).
Step by step solution
01
Identify the Rectangular Coordinates
The given rectangular coordinates in the problem are: \( x = -\frac{\sqrt{3}}{2}, y = 0, z = -\frac{1}{2} \). These are the values we'll convert to spherical coordinates.
02
Calculate the Radial Distance \( r \)
The radial distance \( r \) is calculated using the formula for the magnitude of the vector: \[ r = \sqrt{x^2 + y^2 + z^2} \]Substitute the values:\[ r = \sqrt{\left(-\frac{\sqrt{3}}{2}\right)^2 + 0^2 + \left(-\frac{1}{2}\right)^2} = \sqrt{\frac{3}{4} + \frac{1}{4}} = \sqrt{1} = 1 \]
03
Calculate the Azimuthal Angle \( \theta \)
The azimuthal angle \( \theta \) is measured from the positive x-axis in the xy-plane. Since \( y = 0 \), it simplifies the formula:\[ \theta = \arctan\left(\frac{y}{x}\right) \]However, since \( x = -\frac{\sqrt{3}}{2} \) and \( y = 0 \), \( \theta \) is either \( 0 \) or \( \pi \). Since the point is on the negative x-axis, \( \theta = \pi \).
04
Calculate the Polar Angle \( \phi \)
The polar angle \( \phi \) is calculated from the positive z-axis:\[ \phi = \arccos\left(\frac{z}{r}\right) \]Substitute the given values: \[ \phi = \arccos\left(\frac{-\frac{1}{2}}{1}\right) = \arccos(-\frac{1}{2}) = \frac{2\pi}{3} \]
05
Write the Spherical Coordinates
The spherical coordinates \( (r, \theta, \phi) \) are now summarized from our calculations:\[ (r, \theta, \phi) = (1, \pi, \frac{2\pi}{3}) \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Rectangular Coordinates
Rectangular coordinates, also known as Cartesian coordinates, are a way to specify a point in a three-dimensional space using three values: x, y, and z. Think of it as a grid system, much like the one used on a map, that helps locate a place.
- The x-coordinate tells you how far to move horizontally from the origin, along the x-axis.
- The y-coordinate shows the vertical movement along the y-axis.
- The z-coordinate indicates movement up or down along the z-axis, adding depth to the position.
Radial Distance Calculation
The radial distance, denoted as \( r \), is a measure of how far a point is from the origin, regardless of direction. It's essentially the length of the vector from the origin to the point, much like a ruler's reading tells you the length of a line.
- This distance is calculated using the formula \( r = \sqrt{x^2 + y^2 + z^2} \).
- It combines the effects of all three coordinates into a single distance.
Azimuthal Angle Theta
The azimuthal angle \( \theta \) is measured in the xy-plane from the positive x-axis. It is essentially like determining the direction of the point on the horizontal plane, similar to how a compass shows direction on a map.
- \( \theta \) is found using \( \theta = \arctan\left(\frac{y}{x}\right) \).
- When \( y = 0 \), this simplifies the situation considerably.
Polar Angle Phi
The polar angle \( \phi \) is taken from the positive z-axis down to the line formed by the point and the origin. Picture it like looking at how high or low the point sits in space relative to the ground.
- \( \phi \) is calculated using \( \phi = \arccos\left(\frac{z}{r}\right) \).
- It helps translate the height component of the point relative to the origin.