21 PS2 Solutions

21 PS2 Solutions - Handout #21 April 19, 2010 CS103 Robert...

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Handout #21 CS103 April 19, 2010 Robert Plummer Problem Set #2—Solutions Section 1.5, exercises on pp.72 - 74 1. Exercise 10, p. 73 (a) I am not sore Modus tollens I did not play hockey yesterday Modus tollens (b) (Sunny or Partly Sunny Monday) (Sunny Friday) resolution (c) Spiders are not insects Universal modus tollens (Rosen, p.72) All dragonflies have six legs Universal instantiation, hypothetical syllogism, universal generalization (d) Homer is not a student universal modus tollens (e) Tofu does not taste good universal modus ponens You only eat what is not healthy univ. inst., contrapositive, hyp. syll., univ. gen. (f) I am hallucinating disjunctive syll. I see elephants running down the road modus ponens 2. Exercise 16, pp. 73-74. (a) 1. x(U(x) D(x)) 2. ¬D(Mia) ---------------------- 3. ¬U(Mia) Universal modus tollens, 1, 2 (see p. 72) 3. U(Mia) D(Mia) Univ. instantiation, 1 4. ¬U(Mia) Modus tollens, 2, 3 (b) Incorrect. Issac's car might be not a convertible and fun to drive. The premises would still be true, but the conclusion would be false.
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21 PS2 Solutions - Handout #21 April 19, 2010 CS103 Robert...

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