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cyclic wanted, 5 points concyclic given

Source: 1989 ITAMO p4

January 31, 2020

geometrycyclic quadrilateralConcyclic

Problem Statement

Points

A,M,B,C,D

are given on a circle in this order such that

A

and

B

are equidistant from

M

. Lines

MD

and

AC

intersect at

E

and lines

MC

and

BD

intersect at

F

. Prove that the quadrilateral

CDEF

is inscridable in a circle.

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