reserve a,b,c,d,x,j,k,l,m,n,o,xi,xj for Nat,
  p,q,t,z,u,v for Integer,
  a1,b1,c1,d1 for Complex;

theorem
  for a be non trivial Nat, p be prime Nat st p > a holds
    not p divides a & not a divides p
  proof
    let a be non trivial Nat, p be prime Nat;
    assume p > a; then
    a,p are_coprime by NAT_6:6,NAT_D:7;
    hence thesis by NTC;
  end;
