Nine Point Circle
Drag the corners of the triangle to move it around.
There are nine points related to any triangle that lie on a circle. These nine points, in lists of three, are:
  • The three midpoints of the sides (light blue dots, to the right)
  • The feet of the altitudes (red dots to the right)
  • The midpoints of the lines from each triangle-vertex to the orthocenter (yellow dots to the right)
Click here to read more about the Nine Point Circle.