# Math Help - Maths

1. ## 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

2. This can be done with the following.
$\begin{array}{l} {1\,A \to B} \\
{2\,\left( {A \to D} \right) \to \left( {C \vee B} \right)} \\ {3\,\neg C} \\
\hline B \\\end{array}$

$4\, \neg B\;\mbox{indirect proof}$
$5\, \neg C \wedge \neg B \;\mbox{conjunction 3 ,4}$

$6\,\neg \left( {A \to D} \right) \equiv A \wedge \neg D\;\mbox{Modus Tollens 2,5}$
$7\, A\;\mbox{simplification 6 }$
$8\, B\;\mbox{Modus Pomens 1,7}$
$9\, B\ \wedge \neg B;\mbox{addition 8,4 }$

3. 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

4. Originally Posted by ads
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.

5. Is there a rule against deleting a question after asking it ?

6. Originally Posted by bobak
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.

7. [/QUOTe]
Originally Posted by bobak
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.

8. Originally Posted by bobak
Is there a rule against deleting a question after asking it ?
Originally Posted by mr fantastic
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.

9. Originally Posted by bobak
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

10. 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

11. Originally Posted by ads
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