nine-point circle

== English == === Alternative forms === nine points circle === Etymology === So called because the circle passes through nine points of interest: the feet of the three altitudes, the centers of the three sides, and the midpoints of the segments which join the triangle's vertices with its orthocenter. === Noun === nine-point circle (plural nine-point circles) That circle which passes through the feet of the altitudes of a given triangle. ==== Further reading ==== nine-point circle on Wikipedia.Wikipedia