这是怎么回事？

t=0:pi/500:40*pi
syms t1 t2
x=sin(t1)*cos(t2);
y=sin(t1)*sin(t2);
z=cos(t1);
ezmesh(x,y,z,[0,2*pi,0,4*pi])
hold on
x=1+sin(t1)*cos(t2);
y=1+sin(t1)*sin(t2);
z=1+cos(t1);
ezmesh(x,y,z,[0,2*pi,0,4*pi])
hold on
x='3^1/2'/2*cos(t1)*cos(t2)-1/2;
y='3^1/2'/2*cos(t1)*sin(t2)-1/2;
z='3^1/2'/2*sin(t1)-1/2;3
plot(x,y,z,'b-');
hidden off