5

Part of 2012 ITAMO

Problems(1)

locus of P: APB+CPD=180

Source: ItaMO 2012, P5

ABCD

is a square. Describe the locus of points

P

, different from

A, B, C, D

, on that plane for which

\widehat{APB}+\widehat{CPD}=180^\circ

geometrycircumcirclegeometric transformationreflectionsymmetrygeometry proposed