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AQ+QB independent of points P, A

Source: Mathematics Regional Olympiad of Mexico West 2016 P3

September 7, 2022
geometryfixed

Problem Statement

A circle ω\omega with center OO and radius rr is constructed. A point PP is chosen on the circumference ω\omega and a point A is taken inside it, such that is outside the line that passes through PP and OO. Point BB is constructed, the reflection of AA wrt OO. and PP' is another point on the circumference such that the chord PPPP' is perpendicular to PAPA. Let QQ be the point on the line PPPP' that minimizes the sum of distances from AA to QQ and from QQ to BB. Show that the value of the sum of the lengths AQ+QBAQ+QB does not depend on the choice of points PP or AA