Binormal
The straight line passing through a point of a curve L perpendicular to the osculating plane to L at M_0. If \mathbf r=\mathbf r(t) is a parametrization of L, then the vector equation of the binormal at M_0 corresponding to the value t_0 of the parameter t has the form
\mathbf S(\lambda)=\mathbf r(t_0)+\lambda[\mathbf r'(t_0),\mathbf r''(t_0)].
Comments
This definition holds for space curves for which \mathbf r''(t_0) does not depend linearly on \mathbf r'(t_0), i.e. the curvature should not vanish.
For curves in a higher-dimensional Euclidean space, the binormal is generated by the second normal vector in the Frénet frame (cf. Frénet trihedron), which is perpendicular to the plane spanned by \mathbf r'(t_0) and \mathbf r''(t_0) and depends linearly on \mathbf r'(t_0),\mathbf r''(t_0),\mathbf r'''(t_0) (cf. [a1]).
References
[a1] | M. Spivak, "A comprehensive introduction to differential geometry" , 2 , Publish or Perish (1970) pp. 1–5 |
Binormal. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Binormal&oldid=49668