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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,685

A new page: Set Symbols

What do you guys think of it? Any mistakes?

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Hi MIF;

Looks pretty good. I am not following how to get the complement of A as {1,9}.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,648

I think you defined C and D but forgot A. Although you only use A in 1 example so you can just write D complement instead.

*Last edited by ShivamS (2014-11-17 13:34:24)*

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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,685

Good point, will amend.

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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**ganesh****Administrator**- Registered: 2005-06-28
- Posts: 25,313

Hi MathsIsFun,

I think the symbols/notations are exhausted! Great job!

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**anonimnystefy****Real Member**- From: Harlan's World
- Registered: 2011-05-23
- Posts: 16,037

Hi MIF

Not sure if that's the general case, but I've seen the bolded "I" be used mostly for irrational numbers.

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Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

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**MathsIsFun****Administrator**- Registered: 2005-01-21
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Has anyone else seen I used for irrationals?

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,366

hi MathsIsFun,

Good page.

: is also used to mean 'such that'.

http://en.wikipedia.org/wiki/List_of_ma … al_symbols

The complement of a set only has meaning if the 'universe' is defined.

http://en.wikipedia.org/wiki/Complement_(set_theory)

so you could have: if **U**, the universe, = {1,2,3,4,5,6,7,8,9} and A = {2,3,4,5,6,7,8} then Asuperscriptc = {1,9}

There does not appear to be a regularly used symbol for the irrationals. Wolfram and Wiki do not have one. Maths Exchange has several suggestions (none of which I've ever seen used) but R−Q would seem to do the job.

Bob

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**MathsIsFun****Administrator**- Registered: 2005-01-21
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Great, will add : and define a Universal Set for the Complement example.

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**anonimnystefy****Real Member**- From: Harlan's World
- Registered: 2011-05-23
- Posts: 16,037

Also, A\B can be used to mean A-B.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

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**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,648

You might also want to include some symbols like the symmetric difference, relative complement and aleph-null.

MathsIsFun wrote:

Has anyone else seen I used for irrationals?

No, but neither have I seen "I" represent the "set of imaginary numbers".

bob bundy wrote:

There does not appear to be a regularly used symbol for the irrationals.

I believe the standard is R-Q. Q with a horizontal line on it, or R\Q.

*Last edited by ShivamS (2014-11-18 07:26:28)*

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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,685

Thanks!

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