EXERCISE 5.14 Tautological equivalence AB amounts almost to the fact that A and B have the same interpretation. We have to make the meaning of this "almost" more precise. (1) Show that neither of the two relations AB and A=B imply the other, i.e., give examples of A and B such that (a) AB but A=B and (b) A=B but not AB. (Hint: Use extra/different propositional variables not affecting the truth of the formula.) (2) Explain why the two relations are the same whenever A and B contain the same variables. (3) Finally explain that if A=B then there exists some formula C obtained from B by "renaming" the propositional variables, such that AC