[math-fun] Multiplicativity of arccos identities

Two identities of the form A*arccos(B/C) + D*arccos(E/F) = G*(180 degrees=pi radians) (A,B,C,D,E,F,G integer) having the SAME (A,D), can be "multiplied" to produce a third with that same A,D also. That is, using the complex number formulation, see https://dl.dropboxusercontent.com/u/3507527/AcosMiracles128.out you multiply the corresponding complex numbers M3=M1*M2, N3=N1*N2. This multiplication does not always "work" in the sense that it often yields, say, non-integer B or E. However, "squaring" always works. This partially explains the "powers of 2,3,5" observation. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)