E1 = X1+Y1 E2 = X2+Y2 B = X1*X2 XX1XX2 = B^2 Y1Y2 = Y1*Y2 F = 1+XX1XX2 G = 2*B t0 = E1*E2 t1 = t0-B X3 = t1-Y1Y2 t2 = a*G t3 = Y1Y2+t2 t4 = XX1+XX2 t5 = t4*G t6 = F*t3 Y3 = t6+t5 Z3 = 1-XX1XX2 XX3 = X3^2 ZZ3 = Z3^2 t7 = X3+Z3 t8 = t7^2 t9 = t8-XX3 R3 = t9-ZZ3