Assignment 15 qa

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course Mth 151

05/06/20111206

If your solution to stated problem does not match the given solution, you should self-critique per instructions at

http://vhcc2.vhcc.edu/dsmith/geninfo/labrynth_created_fall_05/levl1_22/levl2_81/file3_259.htm

.

Your solution, attempt at solution. If you are unable to attempt a solution, give a phrase-by-phrase interpretation of the problem along with a statement of what you do or do not understand about it. This response should be given, based on the work you did in completing the assignment, before you look at the given solution.

015. Conditionals

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Question: `q001. There are 6 questions in this set.

The proposition p -> q is true unless p is true and q is false. Construct the truth table for this proposition.

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Your solution: THE TABLE WOULD FOLLOW LIKE THIS:

TTT / TFF / FTT / FFF

confidence rating #$&*: 3

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Given Solution:

The proposition will be true in every case except the one where p is true and q is false, which is the TF case. The truth table therefore reads as follows:

p q p -> q

T T T

T F F

F T T

F F T

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Self-critique (if necessary): I GOT THE LAST ROW INCORRECT. I THOUGHT THERE WAS A SITUATION WHERE IT WOULD CREATE ALL NEGATIVE RESULTS

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Self-critique Rating:3

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Question: `q002. Reason out, then construct a truth table for the proposition ~p -> q.

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Your solution: THE TABLE WOULD READ AS FOLLOWS:

TTFT / TFFT / FTTT / FFTT

confidence rating #$&*:3

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Given Solution:

This proposition will be false in the T -> F case where ~p is true and q is false. Since ~p is true, p must be false so this must be the FT case. The truth table will contain lines for p, q, ~p and ~p -> q. We therefore get

p q ~p ~p -> q

T T F T since (F -> T) is T

T F F T since (F -> F) is T

F T T T since (T -> T) is T

F F T T since (T -> F) is F

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Self-critique (if necessary):N/A

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Self-critique Rating:3

@& For a disjunction it would be so, but not for the conditional.*@

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Question: `q003. Reason out the truth value of the proposition (p ^ ~q) U (~p -> ~q ) in the case FT (i.e., p false, q true).

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Your solution: (p ^ ~q) WOULD BE FALSE. TO BE TRUE IT WOULD NEED TO READ (P ^ Q). ASSUMING THAT FT MEANS FALSE TRUE,

@& F T means the p is false and q is true.*@

(~p -> ~q ) THIS WOULD BE INCORRECT AS WELL. WE WOULD NEED TO TAKE THE OPPOSITE OF THAT TO MAKE IT TRUE. SINCE BOTH ARE FLASE, THE (p ^ ~q) U (~p -> ~q ) IS FLASE

confidence rating #$&*:

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Given Solution:

To evaluate the expression we must first evaluate p ^ ~q and ~p -> ~q.

p ^ ~q is evaluated by first determining the values of p and ~q. If p is false and q true, then ~q is false. Thus both p and ~q are false, and p ^ ~q is false.

~p -> ~q will be false if ~p is true and ~q is false; otherwise it will be true. In the FT case p is false to ~p is true, and q is true so ~q is false. Thus it is indeed the case the ~p -> ~q is false.

(p ^ ~q) U (~p -> ~q ) will be false if (p ^ ~q) and (~p -> ~q ) are both false, and will otherwise be true. In the case of the FT truth values we have seen that both (p ^ ~q) and (~p -> ~q ) are false, so that (p ^ ~q) U (~p -> ~q ) is false.

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Self-critique (if necessary): I AM NOT SURE IF I GOT THIS PROBLEM CORRECT. CAN YOU PLEASE ADVISE

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Self-critique Rating:2

@& See my note. In any case your reasoning on the solution appears to be correct overall.*@

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Question: `q004. Construct a truth table for the proposition (p ^ ~q) U (~p -> ~q ).

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Your solution: THE TABLE WOULD READ AS FOLLOWS:

TTFFTTT / TFFTTTT / FTTFFFF/ FFTTFFT

confidence rating #$&*: 3

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Given Solution:

We will need headings for p, q, ~p, ~q, (p ^ ~q), (~p -> ~q ) and (p ^ ~q) U (~p -> ~q ). So we set up our truth table

p q ~p ~q (p ^ ~q) (~p -> ~q ) (p ^ ~q) U (~p -> ~q )

T T F F F T T

T F F T T T T

F T T F F F F

F F T T F T T

To see the first line, where p and q are both T, we first see that ~p and ~q must both be false. (p ^ ~q) will therefore be false, since ~q is false; (~p -> ~q) is of the form F -> F and is therefore true. Since (~p -> ~q) is true, (p ^ ~q) U (~p -> ~q ) must be true.

To see the second line, where p is T and q is F, we for see that ~p will be F and ~q true. (p ^ ~q) will therefore be true, since both p and ~q are true; (~p -> ~q) is of the form F -> T and is therefore true. Since (p ^ ~q) and (~p -> ~q ) are both true, (p ^ ~q) U (~p -> ~q ) is certainly true.

To see the fourth line, where p is F and q is F, we for see that ~p will be T and ~q true. (p ^ ~q) will be false, since p is false; (~p -> ~q) is of the form T -> T and is therefore true. Since (~p -> ~q ) is true, (p ^ ~q) U (~p -> ~q ) is true.

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Self-critique (if necessary): I GOT SOME OF THE TRUTHS WRONG. ROW 2 AND 4 ARE INCORRECT. I FOLLOWED THE WRONG SENARIO

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Self-critique Rating:

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Question: `q005. If we have a compound sentence consisting of three statements, e.g., p, q and r, then what possible combinations of truth values can occur?

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Your solution: SINCE THERE ARE 2 POSSIBILITIES FOR EACH LETTER, WE CAN DO 2 * 2 * 2 = 8. THERE ARE EIGHT DIFFERENT POSSIBLE COMBINATIONS. THEY WOULD READ AS FOLLOWS: TTT, TFT, FTT, FFT, TTF, TFF, FTF, FFF.

confidence rating #$&*: 3

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Given Solution:

A compound statement with two statements p and q has four possible combinations of truth values: TT, TF, FT, FF. Here we also have r, which can be either T or F. So we can append either T or F to each of the possible combinations for p and q.

If r is true then we have possible combinations TT T, TF T, FT T, FF T. If r is false we have TT F, TF F, FT F, FF F. This gives us 8 possible combinations: TTT, TFT, FTT, FFT, TTF, TFF, FTF, FFF.

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Self-critique (if necessary): N/A

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Self-critique Rating:

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Question: `q006. Evaluate the TFT, FFT and FTF lines of the truth table for (p ^ ~q) -> r.

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Your solution: THE TABLE WOULD READ AS FOLLOWS:

TFTTTT / FFTTFT/ FTFFFT

confidence rating #$&*:3

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Given Solution:

We would need column headings p, q, r, ~q, (p^~q) and (p^~q) -> r. The truth table would then read

p q r ~q (p^~q) (p^~q) -> r

T F T T T T

F F T T F T

F T F F F T

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Self-critique (if necessary): I AM GUESSING I NEED TO START PUTTING THE HEADING OF THE TABLE THEN. THEY ARE IN ALL THE GIVEN SOLUTIONS

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Self-critique Rating:3

@& Right. Without the headings I can't tell how you have broken down the statement.*@

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#*&!

&#Good work. See my notes and let me know if you have questions. &#