proposition: Lemma inj1_proj2 : inj1 ** proj2 = 0.
proof: Proof. by apply: val_inj; rewrite /= mul_row_col mulmx0 mul0mx addr0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype perm choice matrix bigop zmodp mxalgebra poly) ssrcomplements stronglydiscrete coherent edr