reserve x,y,z for Real,
  a,b,c,d,e,f,g,h for Nat,
  k,l,m,n,m1,n1,m2,n2 for Integer,
  q for Rational;

theorem
  d divides a & a gcd b = 1 implies d gcd b = 1 by Th15,NEWTON:57;
