proposition: Lemma ex_lim_seq_geom (q : R) : Rabs q < 1 -> ex_lim_seq (fun n => q ^ n).
proof: Proof. move => Hq ; exists 0 ; by apply is_lim_seq_geom. Qed.
imports: Coq(Reals Psatz ssreflect) Rcomplements Rbar Lub Markov Hierarchy