Triangle, Excircles, Angles, 360 degrees
In the figure below, given a triangle ABC,
Ea, Eb, and Ec are the three
excircles, and the points D, E, F,
G, H, J, K, L, and M are the points of tangency. Prove that the
sum of the angles DEF, GHJ, and KLM is 360 degrees.
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