t=var('t')
a=3
b=2
gamma=vector([a*cos(t),b*sin(t)])
gammad=vector([f.diff() for f in gamma])
tau=gammad/gammad.norm()
gammadd=vector([f.diff() for f in gammad])
nu=vector((-gammad[1],gammad[0]))/gammad.norm()
kappa=matrix([gammad,gammadd]).determinant()/gammad.norm()^3
deltadd=kappa*nu
liste_de_plots=[parametric_plot(gamma, (t,0,2*pi), ticks=[a,b])+
arrow(gamma(s),gamma(s)+tau(s), arrowsize=1, color="green")+
arrow(gamma(s),gamma(s)+deltadd(s), arrowsize=1, color="red")
for s in sxrange(0,2*pi,2*pi/200,include_endpoint=True)]
for g in liste_de_plots: g.set_axes_range(-1.1*a,1.1*a,-1.1*b,1.1*b)
animation=animate(liste_de_plots)
animation.show(delay=10)