I have to rely only on SD+ rules

I use the Logic Book.

Show that the following is valid in SD+

Derive Y=Z

1.~Y-> ~Z. Assume

2.~Z->~X. Assume

3~X->~Y. Assume

I got Z->Y but am stumped on getting Y->Z

I tried everything.

I request any help or hints in finishing it.

1 Answer 1


Use the contrapositive. Y->X, X->Z, therefore Y->Z. (you can show this follows by assuming Y and using modus ponens).

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