Let be a curve and let be a fixed point. Let be on and let be the curvature center
at . Let be the point with a line segment parallel and
of equal length to .
Then the curve traced by
is the radial curve of .
It was studied by Robert Tucker in 1864. The parametric
equations of a curve
with radial point and parameterized by a variable are given by

(1)

(2)

Here, derivatives are taken with respect to the parameter .