foot

The perpendicular foot, also called the foot of an altitude, is the point on the leg opposite a given vertex of a triangle at which the perpendicular passing through that vertex intersects the side. The length of the line segment from the vertex to the perpendicular foot is called the altitude of the triangle. When a line is drawn from a point to a plane, its intersection with the plane is known as the foot.

altitude | cathetus | perpendicular | perpendicular bisector | perpendicular bisector theorem | Taylor circle