### Binormal Twisted Curve

Suppose a twisted curve is defined in terms of the arclength s by r(s)=sech(?)cos(s)i+sech(?)sin(s)j+tanh(?)k, where ? is a constant parameter. Determine (i) the tangent t(s), (ii) the normal n(s), (iii) the binormal b(s), (iv) the curvature ?, (v) the torsion Ï?.