Chapter 2: Problem 406
For the following exercises, the cylindrical coordinates of a point are given. Find its associated spherical coordinates, with the measure of the angle \(\varphi\) in radians rounded to four decimal places. $$\left(3,-\frac{\pi}{6}, 3\right)$$
Short Answer
Expert verified
The spherical coordinates are \((\sqrt{18}, 0.7854, -\frac{\pi}{6})\)."
Step by step solution
01
Understand the Cylindrical Coordinates
The cylindrical coordinates given are \((r, \theta, z) = \left( 3, -\frac{\pi}{6}, 3 \right)\). Here, \(r = 3\) is the radial distance from the z-axis, \(\theta = -\frac{\pi}{6}\) is the angular coordinate measure from the positive x-axis, and \(z = 3\) is the height along the z-axis.
02
Convert to Cartesian Coordinates
The conversion from cylindrical to Cartesian coordinates is given by the formulas: \(x = r\cos\theta\), \(y = r\sin\theta\), \(z = z\). Compute these as: - \(x = 3\cos\left(-\frac{\pi}{6}\right) = 3\left(\frac{\sqrt{3}}{2}\right) = \frac{3\sqrt{3}}{2}\)- \(y = 3\sin\left(-\frac{\pi}{6}\right) = 3\left(-\frac{1}{2}\right) = -\frac{3}{2}\)- \(z = 3\)Thus, the Cartesian coordinates are \(\left(\frac{3\sqrt{3}}{2}, -\frac{3}{2}, 3\right)\).
03
Convert to Spherical Coordinates
In spherical coordinates, \((\rho, \phi, \theta)\), we use the following conversions:- \(\rho = \sqrt{x^2 + y^2 + z^2}\)- \(\phi = \arccos\left(\frac{z}{\rho}\right)\)- Use the original \(\theta\) from cylindrical coordinatesCompute:- \(\rho = \sqrt{\left(\frac{3\sqrt{3}}{2}\right)^2 + \left(-\frac{3}{2}\right)^2 + 3^2} = \sqrt{\frac{27}{4} + \frac{9}{4} + 9} = \sqrt{18}\)- \(\phi = \arccos\left(\frac{3}{\sqrt{18}}\right) = \arccos\left(\frac{3}{3\sqrt{2}}\right) = \arccos\left(\frac{1}{\sqrt{2}}\right) = \frac{\pi}{4}\)Thus, the spherical coordinates are \((\sqrt{18}, \frac{\pi}{4}, -\frac{\pi}{6})\).
04
Round \\( heta\\) to Four Decimal Places
We observe that \( \phi = \frac{\pi}{4} \approx 0.7854 \) radians when rounded to four decimal places.
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.
Cylindrical Coordinates
Cylindrical coordinates provide an alternative way of locating a point in three-dimensional space. Picture differentiating points based on a blend of circular motion and elevation, which is exactly what this system does. You have three components to keep track of:
- Radial distance (\(r\)): This is the straight-line distance from the z-axis to the point. It mirrors the radius of a circle.
- Angular position (\(\theta\)): This angle, typically measured in radians, is between a reference direction (usually the positive x-axis) and the projection of the point onto the xy-plane.
- Vertical height (\(z\)): Simply the distance of the point above or below the xy-plane, running parallel to the z-axis.
Spherical Coordinates
Spherical coordinates offer another method to describe a point in 3D space, where location is determined by encoding radius, polar angle, and azimuthal angle. Imagine earth's latitude and longitude combined with altitude—they're quite similar.
- Radial distance (\(\rho\)): The straight line from the origin to the point. It’s akin to our original radial distance in cylindrical coordinates but spatial instead of planar.
- Polar angle (\(\phi\)): This is the angle measured down from the positive z-axis toward the point. It emphasizes elevation.
- Azimuthal angle (\(\theta\)): Identical to its counterpart in cylindrical coordinates. It specifies direction in the xy-plane.
Angle in Radians
Radians provide a more natural measure for angles in mathematics, especially trigonometry and calculus. They're derived directly from the properties of circles—a full circle encompasses an angle of \(2\pi\) radians.
- When you measure an angle in radians, you're essentially calculating the length of the arc mapped out by the angle across a unit circle.
- An angle measured in degrees is converted to radians by multiplying it by \(\frac{\pi}{180}\). Conversely, to go from radians to degrees, multiply by \(\frac{180}{\pi}\).
Coordinate Conversion
Coordinate conversion is a crucial process in mathematics involving the change from one coordinate system to another, allowing for different perspectives and applications.
- The transition from cylindrical to Cartesian coordinates involves straightforward trigonometric relations: \(x = r \cos\theta\), \(y = r \sin\theta\), and \(z = z\).
- To switch from cylindrical to spherical, a recalibration using all three spatial dimensions is needed: employing \(\rho = \sqrt{x^2 + y^2 + z^2}\) and \(\phi = \arccos\left(\frac{z}{\rho}\right)\).
Cartesian Coordinates
Cartesian coordinates are probably the most familiar coordinate system, often used in basic mathematics and physics. They describe a point in space using orthogonal axes.
- x-coordinate: How far to the right (or left) a point lies relative to the origin along the horizontal axis.
- y-coordinate: The position up or down along the vertical (in 2D) or depth (in 3D) axis.
- z-coordinate: The placement forth and back along the axis perpendicular to both the x and y axes in 3D.