Autodesk AUTOCAD 2006, Command Reference Manual, Page: 229 / 1490

>> Expression: ang(end,end,end)
Select the apex of the angle, and then select the two opposite vertices.
Calculate a Normal Vector
The nor function calculates the unit normal vector (a vector perpendicular
to a line or plane), not a point. The vector defines the direction of the normal,
not a location in space. You can add this normal vector to a point to obtain
another point.
nor
Determines the three-dimensional unit normal vector of a selected circle,
arc, or polyline arc segment. This normal vector is the Z coordinate of the
object coordinate system (OCS) of the selected object.
nor(p1,p2)
Determines the 2D unit normal vector to line p1,p2. The line is oriented
from p1 to p2. The orientation of the resulting normal vector points to the
left from the original line (p1,p2).
nor(p1,p2,p3)
Determines the 3D unit normal vector to a plane defined by the three points
p1, p2, and p3. The orientation of the normal vector is such that the given
points go counterclockwise with respect to the normal.
nor(v)
Determines the two-dimensional unit normal vector to vector v. Both vectors
are considered 2D, projected on the XY plane of the current UCS. The
orientation of the resulting normal vector points to the left of the original
vector v.
The following illustrations show how normal vectors are calculated:
Calculate a Normal Vector | 205