Ken's Puzzle of the Week

A Hidden Hexagon

In the figure, triangles ABC, DEF, and GHJ are congruent isosceles triangles.  Angles B and C are 80 degrees.  Points AEFC, EHJD, DFB, and GHF are collinear.  Without drawing a circle, show how to mark the corners of a perfect hexagon on the diagram, using only a compass set to a constant length.  Prove it's a perfect hexagon.

Source: Original. (Original Visio of graphic.)

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