Polar coordinates are an alternative to the regular xy coordinate system. Instead of expressing x and y we instead express them in terms of trigonometry functions.
This can be especially helpful with functions, limits, and double integrals that are hard to evaluate in the regular coordinate system.
Cylindrical coordinates are an extension of polar coordinates to be used in 3 dimensions instead of just 2, while spherical coordinates are used for solids more spherical in nature.
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