Conical coordinates are a threedimensional orthogonal coordinate system consisting of concentric spheres (described by their radius r) and by two families of perpendicular cones, aligned along the z and xaxes, respectively.
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The conical coordinates (r,μ,ν) are defined by
with the following limitations on the coordinates
Surfaces of constant r are spheres of that radius centered on the origin
whereas surfaces of constant μ and ν are mutually perpendicular cones
In this coordinate system, both Laplace's equation and the Helmholtz equation are separable.
The scale factor for the radius r is one (h_{r} = 1), as in spherical coordinates. The scale factors for the two conical coordinates are
