The curvature and torsion: how to distinguish the shape of a curve 
Still curvature and torsion (IV)
If the zeros of the curvature function are not all isolated, it is not necessary to choose the Frenet-Serret frame at all points where the curvature is zero.
Check in the 3D app (\(k \geq0\)), in which points it is necessary to choose the Frenet-Serret frame in order to have a unique (\(C^{2}\)) curve.
To know more about curvature and torsion...
