recip_den_num@{} q : / ' q = (' den q) / 'num q. Proof. apply path;red;simpl. unfold Frac.dec_rec;simpl. destruct (decide_rel paths (num q) 0) as [E|E];simpl. - rewrite (mult_0_r (Azero:=Azero)), 2!mult_0_l. reflexivity. - rewrite mult_1_l,mult_1_r. reflexivity. Qed.
Require Import HoTT.HIT.quotient. Require Import Import Frac.