Problem 19: Isosceles Right Triangle, Excenter, Perpendicular, Congruence. Level: High School, SAT Prep, College geometry

In isosceles triangle ABC (AB = BC), angle B is a right angle. D is the excenter, BE is drawn perpendicular to AD. Prove that AD = 2BE. Post a comment or solution.
 

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Right triangle, altitude, incircles and inradii.

Problem 18.
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Problem 17.
Right triangle, altitude, and angles.