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show concyclic, common chords of intersecting circles

Source: Mongolia 1999 Grade 8 P6

May 4, 2021

geometry

Problem Statement

Two circles in the plane intersect at

C

and

D

. A chord

AB

of the first circle and a chord

EF

of the second circle pass through a point on the common chord

CD

. Show that the points

A,B,E,F

lie on a circle.