>

restart;

>	with(plots):

Warning, the name changecoords has been redefined

>	a:=2;b:=5;c:=sqrt(a^2+b^2);t:=3*s;

>	r:=c+a*cos(t);

>	x1:=r*cos(s);y1:=r*sin(s);z1:=a*sin(t);

>	r:=c+a*cos(t+Pi);

>	x2:=r*cos(s);y2:=r*sin(s);z2:=a*sin(t+Pi);

>	w:=expand((1-u)*[x1,y1,z1]+u*[x2,y2,z2]);

>	plot3d(w,u=0..1,s=0..2*Pi,scaling=constrained,grid=[5,150]);

>

>