intros; simplify;
split; intro;
apply (.= e1);
- [ apply e | apply (e \sup -1) ]
+ [ apply e | apply (e^-1) ]
| unfold setoid1_of_setoid; simplify;
intros; split; intros 2; simplify in f ⊢ %; apply trans;
[ apply a |4: apply a'] try assumption; apply sym; assumption]