t0 = Y1-X1 t1 = Y2+X2 A = t0*t1 t2 = Y1+X1 t3 = Y2-X2 B = t2*t3 t4 = 2*T2 C = Z1*t4 D = 2*T1 E = D+C F = B-A G = B+A H = D-C X3 = E*F Y3 = G*H T3 = E*H Z3 = F*G