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I triangle geometry, a central triangle is a triangle in the plane of the reference triangle the trilinear coordinates of whose vertices relative to the reference triangle are expressible in a certain cyclical way in terms of two functions having the same degree of homogeneity. At least one of the two functions must be a triangle center function. The excentral triangle is an example for a central triangle. The central triangles have been classified into three types based on the properties of the two functions.