The cartesian equation referred to the axis and directrix is y=c cosh (x/c) or y = **Zc**(e x / c +e x / c); other forms are s = c sinh (x/c) and y 2 =c 2 -1-s 2, being the arc measured from the vertex; the intrinsic equation is s = c tan The radius of curvature and normal are each equal to c sec t '.

The displacement of the point C of the body is made up of 10 tangential to the meridian **ZC** and sin 0 ~,1 perpendicular to the plane of this meridian.

83, which c c are 0 and sin 0~ along and perpendicular to the meridian **ZC**, we see that the com ponent angular velocities about the lines B