The 80-80-20 Triangle Problem, A Derivative

ABC is an isosceles triangle with vertex angle ∠BAC = 20° and AB = AC. Point E is on AB such that AE = BC. Find the measure of ∠AEC.

(This problem has been invented by Sergey Yurin, at the time a ninth grade student, and reported in [Knop].



  1. C. Knop, A Story with Geometry, or Nine Solutions to One Problem, Kvant, 1993, no 6

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