Families of surfaces which are mutually orthogonal. Up to three families of surfaces may be orthogonal in three dimensions. The simplest example of three orthogonal surfaces in three dimensions are orthogonal planes, but three confocal conic surfaces are also mutually orthogonal.
Orthogonal Surfaces
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References
Wells, D. The Penguin Dictionary of Curious and Interesting Geometry. London: Penguin, p. 166, 1991.Referenced on Wolfram|Alpha
Orthogonal SurfacesCite this as:
Weisstein, Eric W. "Orthogonal Surfaces." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/OrthogonalSurfaces.html