Fact eq_rect_combine_dist_helper1 : forall a b c d, b * c = d -> (a + b) * c = a * c + d.Fact eq_rect_combine_dist_helper2 : forall a b c d, b * c = d -> a * c + d = (a + b) * c.

Lemma split1_zero : forall sz1 sz2, split1 sz1 sz2 (natToWord _ O) = natToWord _ O.