3 Mar
2011
3 Mar
'11
12:01 p.m.
[Can't believe I'm responding to a Gosper post . . .]
Pi/2 == ArcSin[13/85] + ArcSin[5/13] + ArcSin[8/17] + ArcSin[33/65]
This one is geometrically obvious, from four right triangles in the 2D lattice, following the sequence of points (0,56) (33,56) (48,36) (60,45) (84,13) (84,0) I wonder how many similar identities can be derived just from pulling right triangles from the lattice. -tom