:: deftheorem defines are_perspective ANPROJ_2:def 3 :
for V being RealLinearSpace
for o, u, v, w, u2, v2, w2 being Element of V holds
( o,u,v,w,u2,v2,w2 are_perspective iff ( o,u,u2 are_LinDep & o,v,v2 are_LinDep & o,w,w2 are_LinDep ) );