What symbol do you use for "contradiction"?

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5 years ago#1
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.
5 years ago#2
I use the two implication arrows facing each other.

http://www.ccc.commnet.edu/grammar/ or www.dianahacker.com/rules
5 years ago#3
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."
To read the math in my posts, download https://addons.mozilla.org/en-US/firefox/addon/748 and http://www.gold-saucer.org/mathml/greasemonkey/.
5 years ago#4
Lightning bolt.
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5 years ago#5
[This message was deleted at the request of the original poster]
5 years ago#6

From: PaulMalucciMD | #004
Lightning bolt.

His Majesty, Palex the Third, Emperor of all the Canadas, has spoken. Go forth and spread the word.
5 years ago#7
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

"You have to be 100% behind someone before you can stab them in the back" ~David Brent.
5 years ago#8
I just say it. I try to find a good balance between text and symbols.
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5 years ago#9
I usually say it, but sometimes it's nice to have shorthand.
5 years ago#10
If I don't just say it, then I'll use the arrows:

-> <-
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