The pedal curve of a curve with respect to a fixed point
(called the pedal
point) is the locus of the foot of the perpendicular
from
to a tangent
to
. The parametric equations for a curve
relative to the pedal
point
are given by
|
(1)
| |||
|
(2)
|
A generalization replaces the perpendicular by a line making a fixed angle with the tangent,
where
.
For either consistent choice of the angle, the resulting
locus is obtained from the ordinary pedal curve by a rotation through
and a dilation
by
, both centered at the pedal
point (Sánchez-Ramos et al. 2021, p. 198).
If a curve is the pedal curve of a curve
, then
is the negative pedal curve
of
(Lawrence 1972, pp. 47-48).
When a closed curve rolls on a line, the area between the line and roulette after a complete revolution by any point on the curve is twice the area of the pedal curve (taken with respect to the generating point) of the rolling curve.
