Fixpoint pow (r:CReal) (n:nat) : CReal :=
  match n with
    | O => 1
    | S n => r * (pow r n)
  end.

Lemma CReal_mult_le_compat_l_half : forall r r1 r2, 0 < r -> r1 <= r2 -> r * r1 <= r * r2.