My friend finished making dodecahedrons, and her next project is to make regular icosahedrons (20-sided dice). Again she wants to know: what is the dihedral angle between any two adjacent faces?
Perhaps this can be solved without the use of spherical trig? ;P
Again, the basis for Geodesic geometry is the icosaherdon, the external angle is 63.434948823+180=243.434948823 degrees and the internal angle is 180-63.434948823=116.565051177 degrees.
Solution
