source 2007 Bernstein--Birkner--Lange--Peters parameter cc4 assume cc4 = 4 c c compute XX = X1^2 compute YY = Y1^2 compute ZZ = Z1^2 compute ZZ4 = cc4 ZZ compute D = XX+YY compute DD = D^2 compute H = 2 D(XX-YY) compute P = DD-YY ZZ4 compute Q = DD-XX ZZ4 compute T = H+Q compute TT = T^2 compute U = H-P compute X3 = 2 P U X1 compute Y3 = Q((T+Y1)^2-TT-YY) compute Z3 = U((T+Z1)^2-TT-ZZ)