reserve a,b,c,x,y,z for object,X,Y,Z for set,
  n for Nat,
  i,j for Integer,
  r,r1,r2,r3,s for Real,
  c1,c2 for Complex,
  p for Point of TOP-REAL n;

theorem
  c[100] - c[-100] = |[2,0,0]|
  proof
    c100 - mc100 = |[1--1,Q-Q,Q-Q]| by EUCLID_5:13
    .= |[2,0,0]|;
    hence thesis;
  end;
