source 2007 Bernstein--Lange compute XX = X1^2 compute ZZ = Z1^2 compute w = a ZZ+3 XX compute s = 2 Y1 Z1 compute ss = s^2 compute sss = s ss compute R = Y1 s compute RR = R^2 compute B = (X1+R)^2-XX-RR compute h = w^2-2 B compute X3 = h s compute Y3 = w(B-h)-2 RR compute Z3 = sss