Re: [math-fun] solid angle of trihedron, aka area of spherical triangle

----- you appear to be confused about lengths versus angles. [blithering omitted] ----- This has nothing to do with my mistake. I worked out a correct formula 25 years ago, and wrote it down again on paper when we began discussing it, but was careless when posting to math-fun. Let the 3 unit vectors in R^3 that define the vertices of the spherical triangle be u, v, w at the tri-angles A, B, C, respectively. Then A = arccos( (v-(v*u)u) / ||"||) * ((w-(w*u)u) / ||"|| ), etc., where * denotes dot product. Then solid angle is omega = A + B + C - pi as shown by the Gauss-Bonnet theorem for a geodesic triangle on a surface of constant Gaussian curvature 1, or the spherical nimiety thingie. —Dan