In classical geometry, the "Radial Distance" is a coordinate in polar coordinate systems (r, \(\theta\)). Basically the radial distance is the scalar Euclidean distance between a point and the origin of the system of coordinates.
\(d = \sqrt{r_1^2 + r_2^2 -2r_1r_2\cos{(\theta_1 - \theta_2)}}\), where \(P_1\) and \(P_2\) are two points with polar coordinates \((r_1, \theta_1)\) and \((r_2, \theta_2)\), respectively, and \(d\) is the distance.
