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joi, 8 iulie 2021

Pr. 8529, Romantics of Geometry, Konstantin Knopp, https://www.facebook.com/photo?fbid=10222350205397538&set=gm.4144235069023501

 Inside the regular hexagon ABCDEF there is a point G so that <DGE=60, <CGD=90. DG intersects AB at X. Find AX/XB.

Proof:
G is intersection of the circles (FOE) and (DE) of centers K, L respectively. Let M, N be midpoints of EF, OM; NL is midline of the trapezoid DEMO, that is, NL=3R/4 (R = AB). Easily KN = OM/6=R.sqrt (3)/12, consequently NL/KN=3.sqrt (3), but triangles KNL and XCE are similar, having perpendicular sides, so CE/CX=3.sqrt (3), but CE=R.sqrt (3), thus CX=R/3, hence AX/XB=2, done.


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https://artofproblemsolving.com/community/c6h616123p3670325

 This is my synthetic proof to the subject problem: