The
dynamic geometry figure below shows a triangle ABC with the circumcenter O. If O_{A}, O_{B}, and O_{C}, are the circumcenters of triangles BOC, AOC, and AOB, respectively, prove that lines AO_{A}, BO_{B}, and CO_{C} are concurrent.

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GeoGebra is free and multi-platform dynamic mathematics software for all levels of education that joins geometry, algebra, tables, graphing, statistics and calculus application, intended for teachers and students. Many parts of GeoGebra have been ported to HTML5.

Geometry Problems

Open Problems

Visual Index

Ten problems: 1411-1420

All Problems

Triangle

Circle

Triangle Centers

Circumradius, Circumcenter

Concurrent lines

Classical Theorems

GeoGebra

HTML5 and Dynamic Geometry

iPad Apps

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