Geometry Stumper

[Albert Chan]

Now that we prove CDE is on the same line, here is another challenge:

With DE as diameter of a circle, midpoint K, prove A, B touch the circle.

In other words, prove AK = BK = DK = EK

Geometry talk: the circle touches triangle 2 vertices and 2 excenters.

Edit: this is the prove, try not to peek ... All about Excircles, section 2.2