Parametrized Goldberg's Tristable Polyhedron with 12 Faces

This Demonstration shows a parametrized Goldberg's tristable polyhedron where the faces are 12 isosceles triangles. The apex angle of Goldberg's original construction is slightly more than 103 degrees. A rectangular net is shown for the case of 90 degrees.

There are two Goldberg tristable polyhedra: the one shown here, which has 12 faces, and the one displayed in the Demonstration linked in the Details, which has 20 faces.