MathDB
center of square lies on angle bisector (2007 Estonia Open Junior 2.2)

Source:

March 27, 2020
geometryangle bisectorsquareright angle

Problem Statement

The center of square ABCDABCD is KK. The point PP is chosen such that PKP \ne K and the angle APB\angle APB is right . Prove that the line PKPK bisects the angle between the lines APAP and BPBP.