Barycentric coordinates 
normalized so that they become the areas
of the triangles 
, 
, and 
, where 
is the point whose coordinates have been specified, normalized
by the area of the original triangle 
. This is equivalent to application of the normalization
relation
(Coxeter 1969, p. 218).
See also
Barycentric Coordinates, Exact Trilinear Coordinates, Homogeneous Barycentric Coordinates, Trilinear Coordinates
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References
Coxeter, H. S. M. Introduction to Geometry, 2nd ed. New York: Wiley, p. 218, 1969.
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Cite this as:
Weisstein, Eric W. "Areal Coordinates." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/ArealCoordinates.html