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6

Part of 2023 Moldova EGMO TST

Problems(1)

Prove that $EF$ and $DG$ are perpendicular.

Source: Moldova EGMO TST 2023

2/4/2023
Let there be a square ABCDABCD. Points EE and FF are on sides (BC)(BC) and (AB)(AB) such that BF=CEBF=CE. LInes AEAE and CFCF intersect in point GG. Prove that EFEF and DGDG are perpendicular.
geometry