Dynamic Geometry: Incenter, Incircle, Inradius
The interactive figure above, created with GeoGebra, shows a triangle ABC with angle bisectors AD, BE and EF intersecting at a point called incenter. The incenter is the center of the incircle or inscribed circle. The inradius is the radius of the incircle or inscribed circle.

To explore (show / hide): tap a check box.
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.