The triangle transformation principle gives rules for transforming equations involving an incircle to equations about excircles.
Triangle Transformation Principle
See also
Excircles, IncircleExplore with Wolfram|Alpha
References
Johnson, R. A. Modern Geometry: An Elementary Treatise on the Geometry of the Triangle and the Circle. Boston, MA: Houghton Mifflin, pp. 191-192, 1929.Referenced on Wolfram|Alpha
Triangle Transformation PrincipleCite this as:
Weisstein, Eric W. "Triangle Transformation Principle." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/TriangleTransformationPrinciple.html