proposition: Lemma dualelement_sn_stn_ge_n {n : nat} (i : stn n) : i >= (dualelement (n,, natgthsnn n)).
proof: Proof. rewrite dualelement_defs_eq. simpl. rewrite (@natminuseqn _), minuseq0'. apply idpath. Defined.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Combinatorics.Maybe UniMath.Combinatorics.StandardFiniteSets UniMath.Algebra.Domains_and_Fields UniMath.Algebra.RigsAndRings