source 2007 Bernstein--Lange
unified
assume Z1=1
assume Z2=1
compute H = X2-X1
compute HH = H^2
compute I = 4 HH
compute J = H I
compute r = 2 (Y2-Y1)
compute V = X1 I
compute X3 = r^2-J-2 V
compute Y3 = r (V-X3)-2 Y1 J
compute Z3 = 2 H
