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AC \cap GE =circumcenter of AGP in half regular dodecagon ABCDEFG

Source: 2000 Austria Beginners' Competition p4

October 4, 2022
geometrycircumcircle3D geometrydodecahedron

Problem Statement

Let ABCDEFGABCDEFG be half of a regular dodecagon . Let PP be the intersection of the lines ABAB and GFGF, and let QQ be the intersection of the lines ACAC and GEGE. Prove that QQ is the circumcenter of the triangle AGPAGP.
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