size(7cm,0);
import solids;

currentprojection = orthographic(50,20,25);

real r=4, h=7;
triple pO=(0,0,0), pS=(0,0,h), pA=(r,0,0);
revolution CoRev=cone(pO,r,h,axis=Z,n=2);

draw(surface(CoRev),lightblue+opacity(.5));
draw(CoRev,1bp+blue);

draw(pS--pA);
draw(pS--pO^^pO--pA,dashed);

label("$S$",pS,N);
dot(Label("$O$",align=SE),pO);
dot(Label("$A$",align=SW),pA);
dot(Label("$O'$",align=SE),pS/2);