:: deftheorem defines // ANALOAF:def 1 :
for V being RealLinearSpace
for u, v, w, y being VECTOR of V holds
( u,v // w,y iff ( u = v or w = y or ex a, b being Real st
( 0 < a & 0 < b & a * (v - u) = b * (y - w) ) ) );