module Tetrahedron(L) {
  cylinder(r1=L/sqrt(3), r2=0, h=L*sqrt(6)/3, $fn=3);
}

module Octahedron(L) {
  cylinder(r1=L/sqrt(2), r2=0, h=L/sqrt(2), $fn=4);
  mirror([0,0,1]) cylinder(r1=L/sqrt(2), r2=0, h=L/sqrt(2), $fn=4);
}

Tetrahedron(10);
translate([15,0,0]) Octahedron(10);