Section BigSetOps.
Variables T I : finType.
Implicit Types (U : {pred T}) (P : pred I) (A B : {set I}) (F :  I -> {set T}).
End Curry.

Lemma imset2Ul (A B : {set aT1}) (C : {set aT2}) :
f @2: (A :|: B, C) = f @2: (A, C) :|: f @2: (B, C).