source 2009.04.27 Bernstein assume Z1 = 1 compute SS1 = S1^2 compute CC1 = 1-SS1 compute SC1 = (S1+C1)^2-SS1-CC1 compute E = D1^2 compute F = SC1^2 compute G = a F compute Z3 = 4 E+G compute D3 = 4 E-G compute C3 = 2(F+4 CC1^2)-Z3 compute S3 = 2((SC1+D1)^2-E-F)