Given an original triangle (thick line), find the medial triangle (outer thin line) and its incircle. Take
the pedal triangle (inner thin line) of the medial triangle with the incenter
as the pedal point. Now pick any point on the original
triangle, and connect it to the point located a half-perimeter
away (gray lines). Then the locus of the midpoints of
these lines (the s in the above diagram) is the pedal
triangle.
Medial Triangle Locus Theorem
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References
Honsberger, R. More Mathematical Morsels. Washington, DC: Math. Assoc. Amer., pp. 261-267, 1991.Tsintsifas, G. "Solution to Problem 674." Crux Math. 8, 256-257, 1982.Referenced on Wolfram|Alpha
Medial Triangle Locus TheoremCite this as:
Weisstein, Eric W. "Medial Triangle Locus Theorem." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/MedialTriangleLocusTheorem.html