MathDB

13

Part of 1997 Baltic Way

Problems(1)

Line joining circumcentres is perpendicular to FC

Source: Baltic Way 1997

1/28/2011
Five distinct points A,B,C,DA,B,C,D and EE lie on a line with ∣AB∣=∣BC∣=∣CD∣=∣DE∣|AB|=|BC|=|CD|=|DE|. The point FF lies outside the line. Let GG be the circumcentre of the triangle ADFADF and HH the circumcentre of the triangle BEFBEF. Show that the lines GHGH and FCFC are perpendicular.
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