reserve a,b,s,t,u,lambda for Real,
  n for Nat;
reserve x,x1,x2,x3,y1,y2 for Element of REAL n;
reserve p1,p2,q1,q2 for Point of TOP-REAL n;

theorem :::Th41: :: AFF_1:27
  q1 in Line(p1,p2) & q2 in Line(p1,p2) implies Line(q1,q2) c= Line(p1,p2)
         by RLTOPSP1:74;
