fact: Definition Exercise5_5_conc_aux I g := f (supremum r (fun_image I g)) +c csumb (even_card0_sub I) (fun z => f (infimum r (fun_image z g))) = csumb (odd_card_sub I) (fun z => f (infimum r (fun_image z g))).
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)