Sydler multiplier 30-60

This is part of Sydler’s angle-multiplication machinery, augmented with my decahedra to remove the 45° angles. All its edges have right dihedral angles, except two, in a line with each other, with angles 30° and 60°. * **Version 1**: this model * [Version 2](https://sketchfab.com/3d-models/sydler-multiplier-30-60-version-2-b7f8946fb46344a0921aeb10c0c52b33): one of the decahedra is positioned the other way round, which makes it fit together very neatly. * [Version 3](https://sketchfab.com/3d-models/sydler-multiplier-30-60-better-no-box-028ffb19ab554505a44d4bf69e599908): repositioning the decahedron means that the boxy part at the top forms a complete box, which we can remove.