Recall Example 5.18, in which we defined a well-formed formula (a “wff”) of propositional logic as a variable; the negation (¬) of a wff; or the conjunction/disjunction/implication (∧, ∨, and ⇒) of...

Recall Example 5.18, in which we defined a well-formed formula (a “wff”) of propositional logic as a variable; the negation (¬) of a wff; or the conjunction/disjunction/implication (∧, ∨, and ⇒) of two wffs. Assuming we allow the corresponding new connective in the following exercises as part of a wff, give a proof using structural induction (see Example 5.21 for an example) that any wff is logically equivalent to one using only . .