Anneau de Möbius 
with(plots):a:=1/2:b:=1/3:c:=1/6:d:=2/3:e:=1/3:C:=
4/5:
x0:=(1+d^2*t^2+2*d*e*t^4+e^2*t^6)/2:x:=(a*t+b*t^3+
c*t^5)/x0:y:=(d*t+e*t^3)/x0:z:=-C/x0:t:=tan(tt):
a1:=diff(v1,tt):a2:=diff(v2,tt):a3:=diff(v3,tt):
v1:=diff(x,tt):v2:=diff(y,tt):v3:=diff(z,tt):
b1:=v2*a3-a2*v3:b2:=a1*v3-v1*a3:b3:=v1*a2-a1*v2:
n1:=simplify(v2*b3-b2*v3):n2:=simplify(b1*v3-v1*b3
):n3:=simplify(v1*b2-b1*v2):
dn1:=diff(n1,tt):dn2:=diff(n2,tt):dn3:=diff(n3,tt)
:
c1:=n2*dn3-dn2*n3:c2:=dn1*n3-n1*dn3:c3:=n1*dn2-dn1
facteur:=simplify(sqrt(b1^2+b2^2+b3^2)/(b1*c1+b2*c
2+b3*c3)):
c1:=simplify(c1*facteur):c2:=simplify(c2*facteur):
c3:=simplify(c3*facteur):
ds:=simplify(sqrt(v1^2+v2^2+v3^2)):
s:=a->evalf(Int(ds,tt=0..a,4))/4:
d:=a->plot3d([x/s(a)+u*c1/s(a),y/s(a)+u*c2/s(a)
,(z+2*C)/s(a)+u*c3/s(a)],
tt=-a..a,u=-1/3*s(a)..1/3*s(a),grid=[150,2],style=
patchnogrid):
n:=40:display([seq(d(k*Pi/2.0001/n,50),k=1..n)],or
ientation=[-60,80],lightmodel=light2,insequence=tr
ue);</Text-field></Input><Output><Text-field layout="Maple Plot"><Plot height="400" plot-scale="1.0" plot-xtrans="0.0" plot-ytrans="0.0" type="three-dimensional" width="400"
Il est bien
