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TT2008 Senior A-Level - P4

Source:

September 4, 2010
geometrycircumcircletrapezoidpower of a pointradical axisgeometry proposed

Problem Statement

Let ABCDABCD be a non-isosceles trapezoid. De fine a point A1A1 as intersection of circumcircle of triangle BCDBCD and line ACAC. (Choose A1A_1 distinct from CC). Points B1,C1,D1B_1, C_1, D_1 are de fined in similar way. Prove that A1B1C1D1A_1B_1C_1D_1 is a trapezoid as well.
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