Adding Vectors (r, θ, φ) - A Step-by-Step Guide

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SUMMARY

To add two vectors in spherical coordinates, represented as (r1, θ1, φ1) and (r2, θ2, φ2), the most effective method is to convert them into rectangular coordinates (x, y, z). After performing the addition in Cartesian coordinates, the result can be transformed back into spherical coordinates. Alternatively, a geometric approach can be employed by constructing a triangle using the vectors, where the lengths of two sides and the angle between them can be determined using the sine and cosine laws, although calculating the angle can be complex.

PREREQUISITES
  • Understanding of spherical coordinates and their representation
  • Knowledge of Cartesian coordinates and conversion techniques
  • Familiarity with trigonometric laws, specifically sine and cosine laws
  • Basic geometric principles related to triangle construction
NEXT STEPS
  • Study the conversion process from spherical to Cartesian coordinates
  • Learn about the sine and cosine laws in triangle geometry
  • Explore vector addition in three-dimensional space
  • Investigate applications of spherical coordinates in physics and engineering
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Students and professionals in mathematics, physics, and engineering who require a solid understanding of vector addition in spherical coordinates, as well as those interested in geometric interpretations of vector operations.

Philosophaie
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How do you add two vectors:

Code:
(r1, theta1, phi1) + (r2, theta2, phi2)

I know if you break them down into x, y, z components you get the right answer but how do you add these vectors.
 
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As you said, transform them to rectangular coordinates (xyz-components), add them, and then transform back to spherical coordinates.
 
If you mean "without using components" (i.e. the hard way) you use trigonometry.

Draw a line segment with one end at (0, 0, 0) in the direction given by theta1 and phi1 with length r1. At its tip, draw a second line segment in the direction given by theta2 and phi2 with length r2. Finally, draw the line segment from (0, 0, 0) to the tip of the second line segment. This forms a triangle in which you know the length of two sides and the angle between them so can use the sine and cosine laws to determine the length and angles of the third side. It is determining the angle between the two sides that is complicated.
 

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