proposition: Lemma oprod2_simpl1 a c: ordinalp a -> \0o <o c -> c *o a = c -> a = \1o.
proof: Proof. move => sa sb. rewrite -{2} (oprod1r (proj32_1 sb)) => sc. by rewrite (oprod2_simpl sa OS1 sb sc). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)