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Math Help - Maths

  1. #1
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    logic

    to all sorry did not know that had accidentally deleted my question
    not trying to do ne thing wrong

    here is my question again


    This rule states the A=>C we can get A=> (A and C)

    Therefore Show that A,C,D and B are propositions , the conclusion B can be inferred from
    A=>B
    (A=>D) => (C or B)
    (A and B) notD,
    Not C
    Last edited by ads; March 1st 2008 at 05:18 PM.
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  2. #2
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    This can be done with the following.
    \begin{array}{l}   {1\,A \to B}  \\<br />
   {2\,\left( {A \to D} \right) \to \left( {C \vee B} \right)}  \\ {3\,\neg C}  \\<br />
\hline    B  \\\end{array}
    4\, \neg B\;\mbox{indirect proof}
    5\, \neg C \wedge  \neg B \;\mbox{conjunction 3 ,4}

    6\,\neg \left( {A \to D} \right) \equiv A \wedge \neg D\;\mbox{Modus Tollens 2,5}
    7\, A\;\mbox{simplification 6 }
    8\, B\;\mbox{Modus Pomens 1,7}
    9\, B\ \wedge \neg B;\mbox{addition 8,4 }
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  3. #3
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    many thanks for your help

    just wondering wat the line between 3 and 4 with the B under the line is

    and i am also not fimiliar with the symbol that is three lines

    once again many many thanks
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  4. #4
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    Quote Originally Posted by ads View Post
    just wondering wat the line between 3 and 4 with the B under the line is and i am also not fimiliar with the symbol that is three lines
    "just wondering wat the line between 3 and 4 with the B under the line is"
    That means therefore B is is true or B follows from those propositions.

    "with the symbol that is three lines" means equivalent to.
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  5. #5
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    Is there a rule against deleting a question after asking it ?
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  6. #6
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    Quote Originally Posted by bobak View Post
    Is there a rule against deleting a question after asking it ?
    I don't know about a rule, but I personally think it's poor form to delete or significantly alter a question once it's been replied too.

    Often though it won't really matter because the wise replier always quotes the post they are replying too.
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  7. #7
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    [/QUOTe]
    Quote Originally Posted by bobak View Post
    Is there a rule against deleting a question after asking it?
    The question is why would one want to do that?
    I can answer that question. I know of at least two “private boarding schools” in the American South that have a stick rule, an honor code violation, against using such a site as this. Such a school in my community will expel such a student. That student’s parents stand to loose a great deal of money the year’s cost is not refundable.
    Asking for a thread to be deleted is just a red flag.
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  8. #8
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    Quote Originally Posted by bobak View Post
    Is there a rule against deleting a question after asking it ?
    Quote Originally Posted by mr fantastic View Post
    I don't know about a rule, but I personally think it's poor form to delete or significantly alter a question once it's been replied too.

    Often though it won't really matter because the wise replier always quotes the post they are replying too.
    The question is why would one want to do that?
    I can answer that question. I know of at least two “private boarding schools” in the American South that have a stick rule, an honor code violation, against using such a site as this. Such a school in my community will expel such a student. That student’s parents stand to loose a great deal of money the year’s cost is not refundable.
    Asking for a thread to be deleted is just a red flag.
    Yes there is a rule against deleting questions. He apologized and restored the original question.
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  9. #9
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    Quote Originally Posted by bobak View Post
    Is there a rule against deleting a question after asking it ?
    If there is a reason to conceal the fact that you asked a question here, then
    don't ask it. The very reason for wanting to delete it means that you may
    well have broken one of our rules even if we did not write it down.

    We frown on academic fraud, cheating on take home tests etc. If we
    discover that is what someone has been doing we will denounce them to
    their institution if possible.

    The answer though is no, but you do not have the power to delete the
    thread once someone has replied, and most helpers will quote your
    question. So even if you edit out the question in your original post it will
    still be visible for all the world to see, and search engines to find.

    RonL
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  10. #10
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    To all i have already stated, but i will do it again beascue i feel bad,

    i did not mean to deletd my post, i have already put it back and have learnt my lesson ( aswell as getting in trouble from the admins)

    so once again sorry
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  11. #11
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    Quote Originally Posted by ads View Post
    To all i have already stated, but i will do it again beascue i feel bad,

    i did not mean to deletd my post, i have already put it back and have learnt my lesson ( aswell as getting in trouble from the admins)

    so once again sorry
    Don't worry about it ..... you've triggered a more general discussion which is NOT aimed at you. It's all gone a bit off-topic - don't be surprised if this thread gets locked soon. Don't feel bad. And again, don't worry about it
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