On 2018-10-27 14:17, James Buddenhagen wrote:
To make the pentagram with all right angles and edges equal pieces of great circles on the surface of a sphere the central angle of each edge is t, where cos(t) = (1-sqrt(5))/2 = -0.618... , about 128.17 degrees.
Thanks. That's a lot less mirificum than I thought. But more deceptive. Maybe it's just my declining comprehension, but I think a lot of web pages have it wrong. Including a paper by Arthur Cayley! —rwg
On Sat, Oct 27, 2018 at 8:05 AM Bill Gosper <billgosper@gmail.com> wrote:
(__agramma is neuter?) I just learned of this. Choose a point on a 2-sphere and traverse 90º of a great circle. Hang a 90º left turn. Traverse another 90º arc. Turn. Iterate. When, if ever, do you return to your starting point? —rwg