Saltire Software

9 Point Circle

The 9 point circle is a circle formed by 9 special points on the triangle. Those points are:

The 3 bases of the altitudes

The midpoint of each side of the triangle

The midpoint of the line segment from each vertex to the orthocenter 

Drag the triangle around to make it bigger. Do the points always form a circle?

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How can you prove that the shape formed by the points is really a circle?

App generated by Geometry Expressions