The interactive figure above, created with GeoGebra, shows a triangle ABC
with the Nine Point Circle or Euler's Circle or Feuerbach Circle.
To manipulate the interactive figure: tap and drag points or lines.
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 explore (show / hide): tap a check box.
Nine Point Circle or Euler's
Circle or Feuerbach Circle
The nine point circle of a triangle ABC is the circle that passes through
nine significant concyclic points: the feet HA, HB, and HC,
of the altitudes,
the midpoints MA, MB, and MC, of each
side and the midpoints EA, EB, and EC of
the segment from each vertex to the orthocenter.
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.