The axis of the accompanying screw motion of a curve $c(s)$ at any point $c(s_0)$ is the line in the direction of the Darboux vector $\tau(s_0) T(s_0) + \kappa(s_0)B(s_0),$ through the point $$P(s_0) = c(s_0) + \dfrac{\kappa(s_0)}{\kappa^2(s_0) +\tau^2(s_0)}N(s_0),$$ where $\kappa, \tau$ are the curvature and torsion functions and $\{T,N,B\}$ is the Frenet frame.
How do I prove this statement??My focus is on the part $P(s_0)$.
I found this statement as part of a problem in the book by W. Kuhnel, Differential Geometry - Curves, Surfaces and Manifolds, Page 53.