Question 1112729
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Assume ~S.  Then from (2), you get ~C v ~D by Disjunctive Syllogism.  Then you can write ~(C & D) from the previous statement using De Morgan.  From this and (3) you get ~R by Modus Ponens.  But, because R is given, that leads to R & ~R which is identically false.  Since the assumption, ~S, led to a contradiction, ~S is false, therefore S.


John
*[tex \LARGE e^{i\pi}\ +\ 1\ =\ 0]
My calculator said it, I believe it, that settles it
<img src="http://c0rk.blogs.com/gr0undzer0/darwin-fish.jpg">
*[tex \Large \ \
*[tex \LARGE \ \ \ \ \ \ \ \ \ \  

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