5
$\begingroup$

This is an example exam question that I'm wondering if I did right? We weren't given an answer key, so I'm checking to make sure I'm comprehending the material and if my answer is correct?

Premises: P $\Rightarrow$ Q, (P $\Rightarrow$ Q) $\Rightarrow$ (T $\Rightarrow$ S), $\lnot$Q, P $\lor$ T

Conclusion: S

My answer:

  1. P $\Rightarrow$ Q: Given

  2. (P $\Rightarrow$ Q) $\Rightarrow$ (T $\Rightarrow$ S): Given

  3. $\lnot$Q: Given

  4. P $\lor$ T: Given

  5. T $\Rightarrow$ S: Modus Ponens 1 and 2

  6. $\lnot$P: Modus Tollens 1 and 3

  7. T: Disjunctive Syllogism 4 and 6

  8. S: Modus Ponens 5 and 7

$\endgroup$
  • 3
    $\begingroup$ It's correct.${}$ $\endgroup$ – Git Gud Feb 16 '15 at 23:02
  • 1
    $\begingroup$ Yep, looks good. $\endgroup$ – Joffan Feb 16 '15 at 23:13
0
$\begingroup$

The proof seems fine. This is a community wiki post so that the question is not marked as unanswered.

$\endgroup$
1
$\begingroup$

This proof is correct according to this proof checker:

enter image description here

Modus ponens is conditional elimination on lines 5 and 8.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.