Solutions to Homework #9, Problems 23-29

1. Modus Tollens: From A ( B and (B infer (A. 1. A ( B. 2. ... so we know that we need to use a ( Intro. The way a ( Intro works is by proving first that the left side implies the right side (by using a ( Intro, assuming the left side, and proving the right side) and then by proving … ................
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