<Li> Barycentric coordinates as used for ternary plots and more generally in the analysis of triangles . </Li> <Li> Trilinear coordinates are used in the context of triangles . </Li> <P> There are ways of describing curves without coordinates, using intrinsic equations that use invariant quantities such as curvature and arc length . These include: </P> <Ul> <Li> The Whewell equation relates arc length and the tangential angle . </Li> <Li> The Cesàro equation relates arc length and curvature . </Li> </Ul>

Who proposed the coordinate system to describe the position of a point in a plane accurately