Binormal Vector
 |  |  | (1) |
 |  | (2) |
where the unit Tangent Vector
and unit ``principal'' Normal Vector 
are defined by | |  | (3) |
 | |  | (4) |
Here,
is the Radius Vector, 
is the Arc Length, 
is the Torsion, and 
is the Curvature. The binormal vector satisfies theremarkable identity | (5) |
References
Kreyszig, E. ``Binormal. Moving Trihedron of a Curve.'' §13 in Differential Geometry. New York: Dover, p. 36-37, 1991.
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