In geometry, an orthocentric system is a set of four points in the plane where one point is the orthocenter of the triangle formed by the other three. // Introduction Geometry (Greek Γεωμετρια, geo = earth, metria = measure ) arose as the field of knowledge dealing with spatial relationships. ... The word point can refer to: a location in physical space a unit of angular measurement; see navigation point is a typographic unit of measure in typography equal inch or sometimes approximated as inch; on computer displays it should be equal to point in typography if the correct display resolution... Plane may refer to: Look up Plane in Wiktionary, the free dictionary An Aeroplane or airplane, a type of fixed-wing aircraft. ... In geometry, an altitude of a triangle is a straight line through a vertex and perpendicular to (i. ... For alternate meanings, such as the musical instrument, see triangle (disambiguation). ...

If four points form an orthocentric system, then each of the four points is the orthocenter of the other three. These four possible triangles will all have the same nine point circle. In geometry, the nine point circle is a circle that can be constructed for any given triangle. ...

The centers of the incircle and excircles of a triangle form an orthocentric system. In geometry, the incircle or inscribed circle of a triangle is the largest circle contained in the triangle; it touches (is tangent to) the three sides. ... In geometry, the incircle or inscribed circle of a triangle is the largest circle contained in the triangle; it touches (is tangent to) the three sides. ...