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Circumcircle and orthocenter

Let P be a point on the circumcircle of triangle ; also let be reflections of P over sides , respectively. Then are all collinear with the orthocenter of the triangle.
  • Points A,B,C are free objects defining triangle ABC & (therefore) the circumcircle.
  • P animates around circle.
  • Orthocenter is point of intersection for all three altitudes of triangle ABC.