球面与柱面的交线值19元？

with(plots): R:=1:
zhumian1:=plot3d([R*sin(u)*cos(v), R*sin(u)*sin(v), R*cos(u)], u=0..Pi, v=0..2*Pi, color=yellow):
zhumian2:=plot3d([(R/2)*(1+cos(t)), (R/2)*sin(t), z], z=-1.1..1.1, t=0..2*Pi, color=green):
z:=(x,y)->sqrt(R^2-x^2-y^2): x:=t->(R/2)*(1+cos(t)): y:=t->(R/2)*sin(t):
quxian1:=spacecurve([(R/2)*(1+cos(t)), (R/2)*sin(t), z(x(t),y(t))], t=0..2*Pi, thickness=5,color=red):
quxian2:=spacecurve([(R/2)*(1+cos(t)), (R/2)*sin(t), -z(x(t),y(t))], t=0..2*Pi,thickness=5,color=red):
display(zhumian1, zhumian2,quxian1,quxian2, scaling=constrained,orientation=[40,65],axes=frame);

感谢分享