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Old 2005-08-21, 19:43   #1
jasong
 
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"Jason Goatcher"
Mar 2005

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Default Weird E-shaped things(serious question)

I've been wanting to study number theory on my own, but have hit a similar snag in all the books I bought from Amazon. I have encountered two symbols, both approximately shaped like a capital letter E. I am going to describe them and hope that someone can give me a link that can adequately explain one or both of them.

The first symbol looks like a letter c with a horizontal line in the middle. The second is a more jagged E. It has a horizontal line at the top, a line going from the left of the top line diagonally to the middle of the letter space, a line going from the middle to the left-bottom, and a horizontal line going to the right from that last diagonal line.

I would really appreciate any help you could give me. thanks
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Old 2005-08-21, 20:12   #2
akruppa
 
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The symbol ∈ mean "is element of". It refers to sets. I.e. if you have a set S = {1,5,9,11}, then 1∈S, but 2∉S (is not an element of).

The ∑ is the sum symbol. There's ususally a variable name and assignment underneath it, and a limit above, kind of like ∑i=110, except they are right below/above the ∑. It means that the term following the ∑ is summed with i going from 1 to 10, i.e.

i=110 i^2 = 1^2 + 2^2 + 3^2 + 4^2 + 5^2 + 6^2 + 7^2 + 8^2 + 9^2 + 10^2

There's a lot more such notation in mathematics, far more than can be explained in a forum. I'm not familiar with english language texts on this, can someone recommend a book that explains some elementary notation?

Alex
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Old 2005-08-21, 20:14   #3
marc
 
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The c sounds like "member of".

See http://en.wikipedia.org/wiki/Member

The second sounds like sigma which would mean "sum of".

See http://en.wikipedia.org/wiki/Sigma
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Old 2005-08-21, 22:44   #4
Orgasmic Troll
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Did you look in the back of the book? Usually there's a page explaining notation. If not, find another book that has one
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Old 2005-08-21, 22:47   #5
Orgasmic Troll
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Hmm. This goes the other way (defintion -> symbol, not symbol -> definition) but it may be helpful to browse: http://mathworld.wolfram.com/topics/Notation.html

ahh, here we go: http://en.wikipedia.org/wiki/Table_o...atical_symbols
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Old 2005-08-22, 00:29   #6
jasong
 
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Thanks anyway, guys. I guess I now know what to look for in a class to take when I go back to college in January, lol!
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Old 2005-08-22, 16:12   #7
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ANSI Unicode characters, according to one source I have:

(Greek capital letter sigma) Σ

(there exists) ∃

(there does not exist) ∄

(element of) ∈

(not an element of) ∉

Last fiddled with by cheesehead on 2005-08-22 at 16:16
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Old 2005-08-22, 16:58   #8
R.D. Silverman
 
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Quote:
Originally Posted by jasong
Thanks anyway, guys. I guess I now know what to look for in a class to take when I go back to college in January, lol!
May I ask where you attended high school? Your failure to recognize
these symbols indicates that your high school teachers were grossly
negligent or incompetent. How can they not teach their students
the symbol for "element of" or "summation"?
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Old 2005-08-22, 17:01   #9
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++ to what Bob said.
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Old 2005-08-22, 17:39   #10
cheesehead
 
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For all your Unicode needs:

"Unicode Home Page" http://www.unicode.org/
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Old 2005-08-22, 17:47   #11
Wacky
 
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Quote:
Originally Posted by R.D. Silverman
May I ask where you attended high school? Your failure to recognize
these symbols indicates that your high school teachers were grossly
negligent or incompetent. How can they not teach their students
the symbol for "element of" or "summation"?
Bob,

Did yours? I do know that it was not a part of my HS math. (in the late '50s)

But times have changed ... By the time that I took Algebra in Grad school, they were introducing Sets to Elementary School students.
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