The figure shows a
square ABCD with center O. It contains arcs AEFC, BFD, and BED
drawn with centers at D, A and C, respectively. Lines CE and FD
meet at G. Prove that the measure of angle DOG is 120 degrees.
![Square, Center, Arc, 120 degrees](p464_square_circle_120.gif)
Dynamic Geometry of Problem 464
Interactive construction created with
GeoGebra by
Tim Brzezinski
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