MathDB

2011.11.4

Part of Kyiv City MO Seniors 2003+ geometry

Problems(1)

equal circumcircles, parallelogram, cyclic (2011 Kyiv City MO 11.4)

Source:

7/15/2020
On the diagonals ACAC and BDBD of the inscribed quadrilateral ABCDBCD, the points XX and YY are marked, respectively, so that the quadrilateral ABXYABXY is a parallelogram. Prove that the circumscribed circles of triangles BXDBXD and CYACYA have equal radii.
(Vyacheslav Yasinsky)
geometrycircumcircleparallelogramequal circlescyclic quadrilateral