Dynamic Geometry 1449: Salmon Line

Given a circle O and three chords AB, AC, and AD. Circles O1, O2, and O3 are constructed with diameters AB, AC, and AD, respectively. Circles O1 and O2 meet at E, Circles O1 and O3 meet at F. Circles O2 and O3 meet at G. Prove that (1) C,G,D are collinear; (2) C,B,E are collinear; (3) B,F,D are collinear) (4) E,F,G are collinear, the line EFG is called the Salmon line.


George Salmon (1819 - 1904) was an Irish mathematician and professor of mathematics at Trinity College Dublin.


Static Diagram of the Salmon Line

Dynamic Geometry 1449: Salmon Line. Using GeoGebra


Poster of the Salmon Line using iPad Apps

Poster of The Salmon Line Dynamic Geometry. Using iPad

Classroom Resource:
Interactive step-by-step animation using GeoGebra

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