MathDB
collinear wanted, circle intersecting a square (2017 Kyiv City MO 8.4)

Source:

September 8, 2020
geometrysquarecollinear

Problem Statement

On the sides BCBC and CDCD of the square ABCDABCD, the points MM and NN are selected in such a way that MAN=45o\angle MAN= 45^o. Using the segment MNMN, as the diameter, we constructed a circle ww, which intersects the segments AMAM and ANAN at points PP and QQ, respectively. Prove that the points B,PB, P and QQ lie on the same line.