proposition: Lemma card_GL_1 : #|'GL_1[F]| = #|F|.-1.
proof: Proof. by rewrite card_GL // mul1n big_nat1 expn1 subn1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg finalg zmodp matrix)