Online Geometry Problem 809: Trisecting a Line Segment AB,
Three Circles,
Radius, Center. Level: High School,
SAT Prep, College,
Mathematics Education

The figure below shows a line segment AB.
Circles with radius AB and centers A and B cut at C and D. Circle with
radius CA and center C cuts AC extended and BC extended at E and F, respectively.
Prove that DE and DF trisect AB
(i.e., AM = MN = NB).