theorem Th4: :: PAPDESAF:4

for V being RealLinearSpace
for OAS being OAffinSpace st OAS = OASpace V holds
for a, b, c, d being Element of OAS
for u, v, w, y being VECTOR of V st a = u & b = v & c = w & d = y holds
( a,b '||' c,d iff u,v '||' w,y )