MathDB

Equal angles in a rhombus

Source: Tuymaada 2013, Day 1, Problem 2 Seniors

July 24, 2013

geometryrhombusgeometric transformationreflectionsymmetrytrapezoidtrigonometry

Problem Statement

Points

X

and

Y

inside the rhombus

ABCD

are such that

Y

is inside the convex quadrilateral

BXDC

and

2\angle XBY = 2\angle XDY = \angle ABC

. Prove that the lines

AX

and

CY

are parallel.
S. Berlov