source 2007 Bernstein--Lange parameter ccd assume ccd = c c d compute XX = X1^2 compute YY = Y1^2 compute ZZ = Z1^2 compute D = XX+YY compute DD = D^2 compute E = 4 (D-ccd ZZ) compute H = 2 D (YY-XX) compute P = DD-XX E compute Q = DD-YY E compute QQ = Q^2 compute X3 = (H+Q) ((Q+X1)^2-QQ-XX) compute Y3 = 2 (H-P) P Y1 compute Z3 = P ((Q+Z1)^2-QQ-ZZ)