Discrete Math Help needed

here’s the theorem that i’m tryin to prove…it’s a basic one, i just wanna be sure that i am doin this right…symbols that i’m usin here, “-” represents “NOT” and “==” represents “IS EQUIVALENT TO”…and of course, “=” is equals, and “:=” represents “is substitued by”…so here it is


Theorem: – p == q == p == --q

Using Distribution of - over ==: - (p == q) == -p == q, for “–p == q” from the theorem; and using Leibniz for the rest of the theorem to carry it down as it is:

= - (- (p == q)) == p == --q

Using Symmetry of == on “p == --q” from the last line: p == q == q == p, where q:= --q; and leibneiz on the rest:

= - (- (p == q)) == --q == p

for “–q == p” from the last line, using Distribution of - over ==: - (p == q) == -p == q, where p:= q, q:= p; and using Leibniz for the rest to carry it down as it is:

= - (- (p == q)) == - (- (p == q))

Reflexivity of == states: p == p; here p:= -( - (p ==q)), therefore intitial theorm is true.


phew

can someone look over it, c if it’s correct? and can someone think of any other ways to prove the theorem??

thanx in advance :slight_smile:


If I’m dreaming, never let me wake. If I’m awake, never let me sleep.

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no one??


If I'm dreaming, never let me wake. If I'm awake, never let me sleep.

ok here’s another one…a lil more complex, but still not 2 bad…just not sure bout the end though…it’s a long one…if anyone has another way of proving this, plz let me know…

symbols that i’m usin here, “-” represents “Not/Negation” ; “–” represents “Double Negation”; “==” represents “Is Equivalent to” ; “=” is “equals” ; “:=” represents “is substitued by” ; “!==” represents “is not equivalent to”…so here it is:


Theorem: ( ( p !== q ) !== r ) == ( p !== ( q !== r ) )

on ( ( p !== q ) !== r ) from the theorem, applying Definition of !==: ( p !== q ) == - ( p == q ) where p:= ( p !== q ) and q:= r ;and Leibniz on the rest:

= - ( ( p !== q ) == r ) == ( p !== ( q !== r ) )

on ( p !== ( q !== r ) ) from the above statement, applying Definition of !==: ( p !== q ) == - ( p == q ) where q:= ( q !== r ) ;and Leibniz on the rest:

= - ( ( p !== q ) == r ) == - ( p == ( q !== r ) )

on ( p !== q ) from the above statement, applying Definition of !==: ( p !== q ) == - ( p == q ) ; and Leibniz on the rest:

= - ( - ( p == q ) == r ) == - ( p == ( q !== r ) )

on ( q !== r ) from the above statement, applying Definition of !==: ( p !== q ) == - ( p == q ) where p:= q, q:= r ; and Leibniz on the rest:

= - ( - ( p == q ) == r ) == - ( p == - ( q == r ) )

on - ( p == q ) from the above statement, applying Distributivity of - over ==: - ( p == q ) == - p == q ; and Leibniz on rest:

= - ( - p == q == r ) == - ( p == - ( q == r ) )

on - ( q == r ) from the above statement, applying Distributivity of - over ==: - ( p == q ) == - p == q where p:= q, q:= r; and Leibniz on rest:

= - ( - p == q == r ) == - ( p == - q == r )

on ( p == - q ) from the above statement, applying Symmetry of ==: p == q == q == p where q:= - q; and Leibniz on rest:

= - ( - p == q == r ) == - ( - q == p == r )

on - ( - p == q == r ), applying Distributivity of - over ==: - ( p == q ) == - p == q where p:= - p, q:= q == r; and Leibniz on rest:

= – p == q == r == - ( - q == p == r )

on - ( - q == p == r ), applying Distributivity of - over ==: - ( p == q ) == - p == q where p:= - q, q:= p == r; and Leibniz on rest:

= – p == q == r == – q == p == r

From Previous Theorem, – p == p, therefore:

= p == q == r == – q == p == r

on – q, applying Theorem: – p == p where p == q; and Leibniz on rest:

= p == q == r == q == p == r

on ( q == p ) from the above statement, applying Symmetry of ==: p == q == q == p; and Leibniz on rest:

= p == q == r == p == q == r

Now here is what i don’t know…

Using the Axiom of Associativity of ==: ( p == ( q == r ) ) == ( ( p == q ) == r ) -----> Is it a valid step??

or

Using Theorem of Relexivity of ==: p == p where p:= p == q == r -----> this should be valid for sure

phew

comeon…where are all the math experts here?? not that an expert is needed for this proof

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If I’m dreaming, never let me wake. If I’m awake, never let me sleep.

sorry dm bhai

all i see that you are messing with the “p” key “r” key and the “equal” key on your keyboard

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unfortunately i dont remember Discrete Maths much

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'cuz its really been a long time (around 5+ yrs)

but for your second proof, wouldnt it be easy if you had used DeMorgan’s law instead…
which i believe is:
-(p AND/OR q) == -p AND/OR -q
and then making use of that Contrapositive logical equivalency…i.e:
p AND/OR q == -q AND/OR -p

ah! cant remember it exactly

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Hang on there brother
i’ll help you in a couple of years

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I did all this crap and I thank God I forgot it all.

Sorry DM, couldn't help you.

[This message has been edited by sambrialian (edited May 12, 2002).]