MathDB
Equal triangles

Source: Greek MO 2013 - P4

May 12, 2013
geometrytrapezoidcircumcircleGreece

Problem Statement

Let a triangle ABCABC inscribed in circle c(O,R)c(O,R) and DD an arbitrary point on BCBC(different from the midpoint).The circumscribed circle of BODBOD,which is (c1)(c_1), meets c(O,R)c(O,R) at KK and ABAB at ZZ.The circumscribed circle of CODCOD (c2)(c_2),meets c(O,R)c(O,R) at MM and ACAC at EE.Finally, the circumscribed circle of AEZAEZ (c3)(c_3),meets c(O,R)c(O,R) at NN.Prove that ABC=KMN.\triangle{ABC}=\triangle{KMN}.