Given a triangle and a point, P, on its circumcircle, the feet of the perpendiculars from P to each of the sides of the triangle (or their extensions) are collinear and define the Simson line. The converse of this is true as well, that if the feet of the perpendiculars from a point P to each of the sides of the triangle (or their extensions) are collinear then P lies on the circumcircle. The line is named after the Scottish mathematician Robert Simson (1687–1768).