MathDB

52

Part of 1988 IMO Longlists

Problems(1)

ABCD is a cyclic quadrilateral

Source: IMO LongList 1988, Mongolia 2, Problem 52 of ILL

11/3/2005
ABCD ABCD is a quadrilateral. A′BCD′ A'BCD' is the reflection of ABCD ABCD in BC, BC, A′′B′CD′ A''B'CD' is the reflection of A′BCD′ A'BCD' in CD′ CD' and A′′B′′C′D′ A''B''C'D' is the reflection of A′′B′CD′ A''B'CD' in D′A′′. D'A''. Show that; if the lines AA′′ AA'' and BB′′ BB'' are parallel, then ABCD is a cyclic quadrilateral.
geometrygeometric transformationreflectiongeometry unsolved