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Dynamic Geometry Problem 987: Triangle, Circumcircle, Incenter, Chord, Parallel, Circle, Tangent. GeoGebra, HTML5 Animation for Tablets (iPad, Nexus). Levels: School, College, Mathematics Education

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The dynamic figure below shows a triangle ABC with the incenter I. AI and BI extended meet the circumcircle Co of triangle ABC at D and E, respectively. DE meets AC at F, chord EG is parallel to FI, FI extended meets DG at K. Prove that the circumcircle of triangle DFK is tangent to circle Co, AC and BK at D, F, and K, respectively.

Dynamic Geometry of Problem 987
The interactive demonstration above was created with GeoGebra.

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GeoGebra
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. It has received several educational software awards in Europe and the USA.
 

  Dynamic Geometry Problem 987: Triangle, Circumcircle, Incenter, Chord, Parallel, Circle, Tangent. GeoGebra, HTML5 Animation for Tablets. GeoGebra, HTML5 Animation for Tablets
 

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