In polar coordinates, the equation of a parabola with parameter and center (0, 0) is given by
(9)
(left figure). The equivalence with the Cartesian form can be seen by setting up a coordinate system and plugging in and to obtain
(10)
Expanding and collecting terms,
(11)
so solving for gives (◇). A set of confocal parabolas is shown in the figure on the right.
In pedal coordinates with the pedal point at the focus, the equation is
(12)
The parabola can be written parametrically as
(13)
(14)
or
(15)
(16)
A segment of a parabola is a Lissajous curve.