What symbol do you use for "contradiction"?

#1Slime_KnightPosted 6/1/2010 2:57:55 PM
We had a topic about which proof mark people use a while ago, and I was just looking at the common contradiction symbols used on http://en.wikipedia.org/wiki/Contradiction#Symbolic_representation . After doing a logic course I pretty much settled on "up tack" (http://www.fileformat.info/info/unicode/char/22a5/index.htm), probably mainly because it's easy to write.
#2Xshortguy007Posted 6/1/2010 4:12:15 PM
I use the two implication arrows facing each other.
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http://www.ccc.commnet.edu/grammar/ or www.dianahacker.com/rules
#3linkkhalid89Posted 6/1/2010 6:26:16 PM
I've seen $\perp,\nleftrightarrow$, as well as two which don't show up in the LaTeX script. But I would use $\Rightarrow\Leftarrow$, although I just generally write "this is a contradiction."
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#4PaulMalucciMDPosted 6/1/2010 6:57:59 PM
Lightning bolt.
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#5Palex3Posted 6/1/2010 8:58:10 PM
[This message was deleted at the request of the original poster]
#6Palex3Posted 6/1/2010 8:58:39 PM

From: PaulMalucciMD | #004
Lightning bolt.


This.
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#7Sir BahamutPosted 6/2/2010 3:49:40 AM
If I'm writing down nicely and neatly I just write "contradiction" or "which gives the required contradiction" or something.

I've gotten quite fond of the lightning bolt for shorthand lately though

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#8avsfan33Posted 6/2/2010 4:13:21 PM
I just say it. I try to find a good balance between text and symbols.
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#9Slime_Knight(Topic Creator)Posted 6/2/2010 6:55:41 PM
I usually say it, but sometimes it's nice to have shorthand.
#10AppleframerPosted 6/4/2010 11:56:13 AM
If I don't just say it, then I'll use the arrows:

-> <-