Module 1 : A Crash Course in Vectors
Lecture 2 : Coordinate Systems
 
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The surface of constant $r$ are spheres of radius $r$ about the centre. the surface of constant $\theta$ is a cone of semi-angle $\theta$ about the z-axis. The reference for measuring $\phi$ is the x-z plane of the cartesian system. A surface of constant $\phi$ is a plane containing the z-axis which makes an angle $\phi$ with the reference plane.
  Example 6
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