Exercises 46–49 establish rules for null quantification that

we can use when a quantified variable does not appear in part

of a statement.

46. Establish these logical equivalences, where x does not

occur as a free variable in A. Assume that the domain is

nonempty.

a) (∀xP (x)) ∨ A ≡ ∀x(P (x) ∨ A)

b) (∃xP (x)) ∨ A ≡ ∃x(P (x) ∨ A)

my doubt is what is exactly “A” in in this logical expressions