An Intrinsic Equation which expresses a curve in terms of its Arc Length and Radius of Curvature (or equivalently, the Curvature ).
See also Arc Length, Intrinsic Equation, Natural Equation, Radius of Curvature, Whewell Equation
Yates, R. C. ``Intrinsic Equations.'' A Handbook on Curves and Their Properties. Ann Arbor, MI: J. W. Edwards, pp. 123-126, 1952.