**Check If Two Boolean Expressions Are Equal**. Outside propositional logic, in order to prove that they are equivalent, you can try to derive the one from the other. You should be able to show that two boolean expressions are equivalent.

In the given solution, stack is used to keep record of the global signs. In general, there are two ways to show that two things are equivalent. (a && b) is equivalent to !a || !b by constructing the truth table below and seeing that they give identical results for the.