# mathmatics and functions

• 10-09-2004
xddxogm3
mathmatics and functions
if I'm defining the range of a function would the following be valid documentation?

Function and rule:

f(x)=x^2

Range f(x) = {f(x)|f(x)>=0}

or is it better to write the range similar to the following.

since,

f(x)=y

then,

Range f(x) = {y|y>=0}

My question is just which is the preferred method of documentation of the mathematician world?
• 10-09-2004
Brain Cell
*EDITED OUT*
• 10-09-2004
Zach L.
This fits in general chat. :)
There are many ways of denoting the range in mathematics. Which one is favored really depends on the branch of mathematics (not all sets that you would want to map a function into have the string ordering, <, or the weak ordering, <=, for example), and on personal preference. I'd be inclined to favor the first version you posted.
• 10-09-2004
Brain Cell
sorry me im REALLY sleepy and i think i misread his post lol. I'll go to sleep before i cause more troubles ;)
• 10-09-2004
Zach L.
Haha... Sleep? What is this you speak of? :D
• 10-09-2004
xddxogm3
thank you.
sorry if my question isn't to clear.
I know two languages.
My native tounge is bad english, but I have been know to talk in a newer dialect called worst english.
;0)
• 10-09-2004
Sang-drax
Of those two notations, I'd prefer the second one.
• 10-09-2004
xddxogm3
so are you people just trying to confuse me because of the new homework post?
I thought my questions on mathmatics have been very clear, and do not ask for you to do the homework for me. now i'm confused, if this is asking to much or violating the homework rule could someone tell me. I do believe both would be technically correct, but the usage would probably be personal preferrence.
• 10-09-2004
Sang-drax
I think the first notation looks very strange. If you want to use f(x), just write:
{f(x)|x€R}
{x^2|x€R}
or
f(x)>=0
Because range(f) is every possible value of f.
• 10-09-2004
Zach L.
I'd be more likely to write something like:
f >= 0 (where the variable is implicit)... but that's just me.

Use which ever notation you prefer (or, which ever one your teacher prefers ;) ).
• 10-09-2004
xddxogm3
Sang-drax
how did you get the element symbol? is that a currency format?
Quote:

{f(x)|x€R}
{x^2|x€R}
thanks for everyones input on this question.
i will be asking my teacher how she wants the answer.
i was just wondering if there was an unstated rule on what was an accepted format among the mathematicians. I feel my question was answered in detail.
• 10-10-2004
Sang-drax
Quote:

Originally Posted by xviddivxoggmp3
Sang-drax
how did you get the element symbol? is that a currency format

The Euro is good for many things, not just for free trade within Europe etc. :)
on European keyboards with Windows, the euro symbol is typed with Alt Gr+E.