A normal line (or simply normal or perpendicular) of a curve at one of its points is the line passing through this point and perpendicular to the tangent line of the curve at . The point is the foot of the normal.
In the case that the tangent is horizontal, the equation of the vertical normal is
and in the case that the tangent is vertical, the equation of the normal is
The normal of a curve at its point always goes through the center of curvature belonging to the point .
In the picture below, the black curve is a parabola, the red line is the tangent at the point , and the blue line is the normal at the point .
|Date of creation||2013-03-22 17:09:53|
|Last modified on||2013-03-22 17:09:53|
|Last modified by||pahio (2872)|
|Synonym||normal of curve|
|Defines||foot of normal|
|Defines||foot of perpendicular|