Let P be a point in the plane of triangle ABC. Denote the reflections of A, B, C about P by A′, B′ and C′, respectively. Let A′′, B′′, C′′ be the reflections of A′, B′, C′ over the lines BC, CA and AB, respectively. Let the line A′′B′′ intersect AC at Ab and let A′′C′′ intersect AB at a point Ac. Denote by ωA the circle through the points A, Ab, Ac. The circles ωB, ωC are defined similarly. Prove that ωA, ωB, ωC are coaxial, i.e., they share a common radical axis.
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