Greatest Triangles: The Triangle Proved Isosceles by Self-Congruence
One entry from the 10 Greatest Triangles countdown: The Triangle Proved Isosceles by Self-Congruence.
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Cartoon by Ben Orlin, Math with Bad Drawings. https://cartoons.mathwithbaddrawings.com/2025-10-08-the-10-greatest-triangles-of-the-21st-century--greatest-triangles-the-triangle-proved-isosceles-by-self-congruence/ (CC BY-NC 4.0)Transcript
#4: The triangle proved isosceles by its congruence to itself. "As angle B = angle C, we deduce △ABC is congruent to △ACB by AAS, and thus AB = AC. One of the first proofs found by computer. A harbinger of things to come."