Normal (geometry) Normal (geometry) In geometry, a normal is an object such as a line or vector that is perpendicular to a given object. For example, in two dimensions, the normal line to a curve at a given point is the line perpendicular to the tangent line to the curve at the point. In three dimensions, a surface normal, or simply normal, to a surface at a point "P" is a vector that is perpendicular to the tangent plane to that surface at "P". The word "normal" is also used as an adjective: a line normal to a plane, the normal component
Polar circle (geometry) Polar circle (geometry) In geometry, the polar circle of a triangle is the circle whose center is the triangle's orthocenter and whose squared radius is where "A, B, C" denote both the triangle's vertices and the angle measures at those vertices, "H" is the orthocenter (the intersection of the triangle's altitudes), "D", "E", "F" are the feet of the altitudes from vertices "A, B, C" respectively, "R" is the triangle's circumradius (the radius of its circumscribed circle), and "a", "b", "c" are the lengths of the triangle's sides opposite vertices "A", "B", "C" respectively. The first parts of the radius