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with(plots):

a:=2.4:

f(x,y):=x^2+y^2;

qumian:=plot3d(f(x,y),y=-sqrt(a^2-x^2)..sqrt(a^2-x^2),x=-a..a,color=yellow):

pingmian:=plot3d(1-x-y,y=-sqrt(a^2-x^2)..sqrt(a^2-x^2),x=-a..a,color=green):

tuoyuan:=spacecurve([-1/2+sqrt(3/2)*cos(t),-1/2+sqrt(3/2)*sin(t),2-sqrt(3/2)*(sin(t)+cos(t))],t=0..2*Pi,thickness=6,color=red):

x_axis:=plot3d([u,0,0],u=-a..a,v=0..0.01,color=blue):

y_axis:=plot3d([0,u,0],u=-a..a+1,v=0..0.01,color=blue):

z_axis:=plot3d([0,0,u],u=-3..8,v=0..0.01,color=blue):

xyz:=display(x_axis,y_axis,z_axis,thickness=3):

display(qumian,pingmian,tuoyuan,xyz,orientation=[50,60],tickmarks=[4,4,4],axes=none,grid=[40,40],lightmodel=light2);

 with(plots):

a:=2.3:

f(x,y):=x^2+y^2;

qumian:=plot3d(f(x,y),y=-sqrt(a^2-x^2)..sqrt(a^2-x^2),x=-a..a,color=blue,style=wireframe):

pingmian:=plot3d(1-x-y,y=-a..a,x=-a..a,color=brown,style=wireframe):

tuoyuan:=spacecurve([-1/2+sqrt(3/2)*cos(t),-1/2+sqrt(3/2)*sin(t),2-sqrt(3/2)*(sin(t)+cos(t))],t=0..2*Pi,thickness=3,color=red):

tuoyuanban:=plot3d([-1/2+r*cos(t),-1/2+r*sin(t),2-r*(sin(t)+cos(t))],t=0..2*Pi,r=0..sqrt(3/2),

scaling=constrained, style=patchnogrid, lightmodel=light1,color=green):

x_axis:=plot3d([u,0,0],u=-a..a,v=0..0.01,color=blue):

y_axis:=plot3d([0,u,0],u=-a..a+1,v=0..0.01,color=blue):

z_axis:=plot3d([0,0,u],u=-1..3,v=0..0.01,color=blue):

xyz:=display(x_axis,y_axis,z_axis,thickness=3):

display(qumian,pingmian,tuoyuan,tuoyuanban,xyz,orientation=[50,60],axes=none);