I am looking at the possibility of carrying on 261C into this next year. Now, this year (261C) I struggled literally the entire year. I reckon this was my hardest subject and must have spent around 3/4 months of the year just doing that subject. In the end I managed to "click" and managed an 83% in the exam.

How does this subject compare to COS261 and any recommendations on the subject?

Thanks,

Kyle]]>

How many are joining me tomorrow in the struggle & where?]]>

What am I missing?]]>

= 2n + 24. All the steps leading up to this makes sense to me. Immediately after this (the final step), they have

>= (n + 1) + 12

the problem is that I dont see how one can transform 2n + 24 into (n + 1) + 12 so this doesnt seem valid to me. I hope I'm just missing something in which case, can some kind soul please point out what that is?]]>

It's the first year with the new syllabus.

I have the solution tutorials - if anyone is interested.

Mail: reanie at netpoint dot co dot za]]>

I don't know if I just missed something in the chapter, but the premise doesn't look like a well formed formula here.

There is nothing to the left of the conditional.

-Valkeye]]>

line 3 puzzles me. It's been a while since I dealt with sums. Does line 3 follow from line 2? By which rule?]]>

valuation (as done in a bottom-up fashion in Fig 1.7 on page 40 in LCS) with the parse tree in

Has any else noticed that there is no Figure 1.23? But there is a Figure 1.3.

I have emailed Mrs Viljoen to confirm the correct Figure to use.]]>

Can anybody please let me know what the assignment dates are for this module or better yet send me a copy of Tut101? I would like to finalize my study schedule for the year and since I only registered for this module today, I have no tut letters and myUnisa has not been updated yet.

Thanks.]]>

I thought parts of it were really very hard. Where did the soundness and completeness theorems come from? That was a curve ball.

JoJ.]]>

I've picked up COS361 this year after doing COS261 back in 2006. Excuse me for being a bit rusty but I just don't seem to get the justification for introducing anything if you've proven a contradiction.

I get and understand the causal relationship for not introduction (p22), which we learnt in the first two years as

The rule states that

From prior in the chapter, it says that any sequent can be converted into a theorem by conjoining all the premises and then implying the conclusion.

ie. p1, p2, p3 |- c

can be rewritten:

|- (p1 ^ p2 ^ p3) --> c

Thus the rule can also be rewritten in the same way as:

|- (

Thus it should follow the same truth table as any other implication

Language: PHPA | B || A -> B ---------------------- F | F || T F | T || T T | F || F T | T || T

If you do the same thing for the the contradiction rule, you get:

Language: PHPcontr | phi || contr -> phi ------------------------------------ F | F || T F | T || T T | F || F T | T || T

The last two lines are nonsensical in terms of a contradiction since contradictions are always false. In this case, the rule cannot complete the truth table for the implication thus it doesn't make sense that the implication is a valid operator. Thus, it doesn't follow that an arbitrary variable can be conjured up if a contradiction occurs.

What does anybody else think?]]>

Line 1 is not labeled as a premise yet it's the only one. There are two arguments running side-by-side from line 2 (I assume this is to save space). Both of these arguments on line 2 (not p in the first argument, and q in the second argument) begin with a premise. This is an error; these are not premises but rather assumptions.]]>