Khan Academy on a Stick
Parametric equations and polar coordinates
An alternative to Cartesian coordinates.

Parametric Equations 1
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Introduction to parametric equations

Parametric Equations 2
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Eliminating the parameter

Parametric Equations 3
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Removing the parameter from a more interesting example

Parametric Equations 4
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Parametric Equations that "move" along the same path
Parametric equations
Here we will explore representing our x's and y's in terms of a third variable or parameter (often 't'). Not only can we describe new things, but it can be super useful for describing things like particle motion in physics.

Polar Coordinates 1
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Introduction to polar coordinates

Polar Coordinates 2
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Conversion from Cartesian to Polar Coordinates

Polar Coordinates 3
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Converting between Cartesian and Polar functions
Polar coordinates
Feel that Cartesian coordinates are too "square". That they bias us towards lines and away from cool spirally things. Well polar coordinates be just what you need!