for p1, p2 being Point of (TOP-REAL 2)
for r1, r2, s1, s2 being Real st p1 = <*r1,s1*> & p2 = <*r2,s2*> holds
( p1 + p2 = <*(r1 + r2),(s1 + s2)*> & p1 - p2 = <*(r1 - r2),(s1 - s2)*> )