(programming required) Given a proposition ϕ, compute the set of all atomic propositions contained within ϕ. The following recursive formulation may be helpful: variables(p) := {p} variables(¬ϕ) :=...

(programming required) Given a proposition ϕ, compute the set of all atomic propositions contained within ϕ. The following recursive formulation may be helpful:

variables(p) := {p} variables(¬ϕ) := variables(ϕ) variables(ϕ ⋄ ψ) := variables(ϕ) ∪ variables(ψ)