intros x; try assumption.
case x; unfold eqfraction, fraction0 in |- *; simpl in |- *.
intros numer denom H' H'0; try assumption.
apply Trans with numer; auto with algebra.
apply Trans with (monoid_unit R); auto with algebra.
Qed.

Lemma eqfraction_sym : symmetric eqfraction.
red in |- *.