Let ABCD be a tangential or circumscribed quadrilateral (see the dynamic figure below). Lines EF and GH intersect at P so that AEPH, BGPE, CFPG and DHPF are circumscribed quadrilaterals. Prove that EF and GH are congruent.
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Ten problems: 1411-1420
Tangential or Circumscribed Quadrilateral
Incircle, Incenter, Inscribed circle
Circle Tangent Line
HTML5 and Dynamic Geometry
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