MathDB
DFG = FCG

Source: KJMO 2023 P2

November 4, 2023
geometrycircumcircle

Problem Statement

Quadrilateral ABCD(AD<BC)ABCD (\overline{AD} < \overline{BC}) is inscribed in a circle, and H(A,B)H(\neq A, B) is a point on segment AB.AB. The circumcircle of triangle BCHBCH meets BDBD at E(B)E(\neq B) and line HEHE meets ADAD at FF. The circle passes through CC and tangent to line BDBD at EE meets EFEF at G(E).G(\neq E). Prove that DFG=FCG.\angle DFG = \angle FCG.