reserve p1,p2,p3,p4,p5,p6,p,pc for Point of TOP-REAL 2;
reserve a,b,c,r,s for Real;

theorem
  p1 in inside_of_circle(a,b,r) & p2 in outside_of_circle(a,b,r) implies
  ex p st p in LSeg(p1,p2) /\ circle(a,b,r) by Lm17;
