reserve c, c1, c2, d, d1, d2, e, y for Real,
  k, n, m, N, n1, N0, N1, N2, N3, M for Element of NAT,
  x for set;

theorem
  for a, b, c being Real st 0 < a & a <= b & c >= 0 holds a to_power c
  <= b to_power c by Lm6;
