- #1

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Sorry, I can't give example, the only places I've seen have been using it informally.

I read,

http://www.reddit.com/r/math/comments/995dl/ask_math_reddit_what_does_the_dot_in_this/

, but can't find a definitive answer.

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- Thread starter PhDorBust
- Start date

- #1

- 143

- 0

Sorry, I can't give example, the only places I've seen have been using it informally.

I read,

http://www.reddit.com/r/math/comments/995dl/ask_math_reddit_what_does_the_dot_in_this/

, but can't find a definitive answer.

- #2

mathman

Science Advisor

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- #3

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So you could substitute arbitrary values for the other arguments with no effect?

Would this be proper (albeit useless) example of usage?

Let function f map R x R to R be defined as f(x,·) = x + 4.

I've always been used to seeing,

Let y be in R. Let function f map R x R to R be defined as f(x,y) = x + 4.

- #4

AlephZero

Science Advisor

Homework Helper

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In elementary algebra, you use variables like "x" to mean "any object of some type" - for example "any real number".

If you want to prove a general theorem in mathematical logic about "all possible functions with 3 arguments, regardless of what the functions actually do or what types of arguments they have", then you need notations to represent ideas like "a general example of such a function", or "any possible values of the first argument of such a function".

That is one use for notations like f(.,.,.) and the "x" part of f(x,.,.).

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