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Assignment 02, Quest 01
April 25, 2006 05:28PM
Hello Everybody,

I've already ordered the prescribed book but unfortunately, due to a misunderstanding with the bookseller , i havn't received it yet. I' already missed the first assignment and I absolutely need to attempt the second one to gain exam sitting.

Since question 1 of assignment02 is from the prescribed book, can you please send me the question.

Thanks a lot,
Anonymous User
Re: Assignment 02, Quest 01
April 28, 2006 12:26PM
The next two exercises present valid arguments. Turn in informal proofs of the arguments' validity. Your proofs should be phrased in complete, well-formed English sentences, making use of first-order sentences as convenient, much in the style we have used above. Whenever you use proof by cases, say so. You don't have to be explicit about the use of simple proof steps like conjunction elimination. By the way,, there is typically more than one way to prove a given result.
(Exercises 5.7 and 5.8 are given, but for the assignment, we just have to do 5.7.)

│Home(max) V Home(claire)
│¬Home(max) V Happy(carl)
│¬Home(claire) V Happy(carl)

Re: Assignment 02, Quest 01
April 30, 2006 03:22PM
Thanks a lot..However I'm still a bit confused.

│Home(max) V Home(claire)
│¬Home(max) V Happy(carl)
│¬Home(claire) V Happy(carl)

Is this the answer to question 1?

Also, can you please give me a hint on question 1.1
I badly need to send my answers before 10 May because I've missed assignment01.

avatar Re: Assignment 02, Quest 01
May 01, 2006 01:23PM
Hey Rajeev

That's not the answer, that's the question. The authors of the textbook use a slightly different notation to that used by Gutenplan from COS161.

To translate:

let P = Max is home
let Q = Claire is home
let R = Carl is happy

Then by Gutenplan's notation, the question becomes

P v Q, ¬P v R, ¬Q v R |- R

The question requires an informal proof which is just basically using ordinary english to create the proof. The textbook give the following as an example of an informal proof:

Since Socrates is a man and all men are mortal, it follows that Socrates is mortal. But all mortals will eventually die, since that is what it means to be mortal. So Socrates will eventually die. But we are given that everyone who will eventually die sometimes worries about it. Hence Socreates sometimes worries about dying.

Hope this helps.
Re: Assignment 02, Quest 01
May 07, 2006 02:20PM
Hello Rob,

Thanks a lot for the hint. Its much clearer now.

Anonymous User
Re: Assignment 02, Quest 01
May 31, 2006 08:52PM
I just started the ass and have to get it in by tonight. Prob is I don't know why I am having such trouble with this ques.
I see the answer to it analytically, but when it comes to actually using the proofs of elim and intro - i'm having trouble.
Any clues would be GREATLY appreciated
avatar Re: Assignment 02, Quest 01
May 31, 2006 09:44PM
You don't use the intro and elim methods here, that's for FORMAL proofs, this question calls for an INFORMAL proof. You should be using ordinary sentences to answer this one.
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