1. A : Type@i'
2. B : Type@i'
3. a : ⇃(A)@i
4. f : A ⟶ ⇃(B)@i
⊢ f a ∈ ⇃(B)
{ DVar `a' }
1. A : Type@i'
2. B : Type@i'
3. a : Base
4. a1 : Base
5. a = a1 ∈ pertype(λx,y. ((x ∈ A) ∧ (y ∈ A) ∧ True))
6. a ∈ A
7. a1 ∈ A
8. True
9. f : A ⟶ ⇃(B)@i
⊢ (f a) = (f a1) ∈ ⇃(B)