u 1 = X 1 Z 2 2 , u 2 = X 2 Z 1 2 ,
s 1 = Y 1 Z 2 3 , s 2 = Y 2 Z 1 3 ,
h = u 2 - u 1 , r = s 2 - s 1 ,
X 3 = - h i> 3 - 2 u 1 h 2 + r 2 ,
Y 3 = - s i> 1 h 3 + r ( u 1 h 2 - X 3 ),
Z 3 = Z 1 Z <...