###### 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. To stop/play the animation: tap the icon in the lower left corner. To reset the interactive figure to its initial state: tap the icon in the upper right corner. To manipulate the interactive figure: tap and drag points or lines.    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.
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