Problem 2 Download Lecture Slides 28, Part I. Do the two exercises on page 14.

Note that, in each of the two exercises, you have to show that I, i.e., that I semantically implies

y. This is a semantic assertion, it is not a formal proof-theoretic assertion, which is written as I p.

So, as a first step in each of the two exercises, you have to explain how you can go from "Ty" to a

set of (closed) first-order wff's to which you can apply the ground tableau method, and then obtain a

closed tableau from which you can draw the desired conclusion.

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