Definition:Torsion of Curve Parameterized by Arc Length/3-Dimensional Real Vector Space
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Definition
Let $\alpha : I \to \R^3$ be a (smooth) curve parameterized by arc length.
Let $s \in I$ be such that the curvature $\map \kappa s \ne 0$.
The torsion of $\alpha$ at $s$ is the real number $\map \tau s$ defined by:
- $\map {b'} s = \map \tau s \map n s$
where:
- $\map {b'} s$ is the derivative of the binormal vector
- $\map n s$ is the normal vector
Also see
Sources
- 2016: Manfredo P. do Carmo: Differential Geometry of Curves and Surfaces (2nd ed.): $1$-$5$: The Local Theory of Curves Parametrized by Arc Length