x(t) = a cos t
y(t) = b sin t
0<b<a
0≦t≦2π
find the arc length parametrization s ├──> (x(s),y(s))
更新1:
using s (arc length) as a parameter so that (x(s),y(s)) and (x(t),y(t)) represent the same curve eg (x(t),y(t)) = (Rcos t,Rsin t) t from 0 to 2Pi (x(s),y(s))=(Rcos(s/R),Rsin(s/R)) s from 0 to 2PiR