End UnitRingTheory.
Arguments invrK {R}.
Arguments invr_inj {R} [x1 x2].
Section UnitRingMorphism.
Variables (R S : unitRingType) (f : {rmorphism R -> S}).

Lemma divr1_eq x y : x / y = 1 -> x = y. Proof. by move/mulr1_eq/invr_inj. Qed.