reserve AFV for WeakAffVect;
reserve a,a9,b,b9,c,d,p,p9,q,q9,r,r9 for Element of AFV;
reserve AFV for WeakAffSegm;
reserve a,b,b9,b99,c,d,p,p9 for Element of AFV;

theorem
  a<>b & not MDist a,b implies ex c st a<>c & a,b // b,c
by Def1;
