LOGIC-KNOWLEDGE-TAKEN-FOR-GRANTED-Q3-ANSWER.html -- ACL2 Version 6.3

### LOGIC-KNOWLEDGE-TAKEN-FOR-GRANTED-Q3-ANSWER

the inductive step of the `rev-rev` proof -- Answer to Question 2

    Major Section:  INTRODUCTION-TO-THE-THEOREM-PROVER

The correct answer to Question 3 in logic-knowledge-taken-for-granted is that you need to prove

    Subgoal to Relieve Hyp 1:
    (implies (and (q (f a))
                  (r a))
             (p (f a)))

in order to use

    Theorem:
    (implies (p (f x))
             (equal (g (h x))
                    x))

to rewrite the target `(g (h a))` to `a` in

    Goal Conjecture:
    (implies (and (q (f a))
                  (r a))
             (s (g (h a))))

If you don't see why, re-read the discussion of rewriting again. Forgetting about the need to relieve hypotheses is a common mistake in informal proofs. ACL2 won't forget to relieve them. But if you forget about the need to do it, you may be confused when ACL2 doesn't see the ``proof'' you see!

Now use your browser's Back Button to return to the end of quiz in logic-knowledge-taken-for-granted.