# What do you call to this?

Discussion in 'Math' started by Lightfire, Feb 17, 2014.

1. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
$
\left\ \frac{df(x)}{dx} \right|_{\small{x=-5}}=4(-5)-6=-26
$

Hmm the line that has x=-5? I'm finding it at MathType but I can't.

2. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
Sorry but I do not ask for the explanation but thanks.

I'm asking what do you call to the symbol "|" because I'm finding it at MathType.

3. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,971
616
It means "plug this value of x" into the function.

You will also see the same thing when dealing with integrals.

4. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
519
Now that you have explained your question, shteii gave you a pretty swift good answer.

More formally it is one symbol used for the mathematical statement

"such that"

You will also find it in the definition of functions, and set theory

eg

A = {x | x>1} read "the set A such that x is greater than 1"
S = {x| x=5} "read the set S such that x=5"

etc

you can also use a colon : {x: x=5}

You will find the symbol | one to the left of the Z key on the ordinary keyboard as well as in Mathtype.

5. ### WBahn Moderator

Mar 31, 2012
20,230
5,755
I think in the context you are using it above it is more appropriate to consider it a "restriction" symbol, which is certainly related. You will usually see it read in these cases as "evaluated at" or "evaluated for", or "restricted to", or "given that". This makes more sense in uses such as you provided. For most people, saying, "The derivative of f(x) with respect to x evaluated at x = -5," is much clearer than saying, "The derivative of f(x) with respect to x such that x = -5." (But I think the latter is technically valid, too; just a bit awkward for most people).

As for the name for the symbol itself (distinct from any context of use), I don't know that it has one. It is usually called the "pipe" symbol (for how it was commonly used when it appeared on computer keyboards way back when) or just the "vertical bar" symbol.

It is used for a number of things in math, not all of them tightly related. But many of those uses are in one way or another a variant on the notion of a "conditional" or a constraint being placed on something.

I just found this:

http://en.wikipedia.org/wiki/Vertical_bar

I never heard of most of those names. Polon? Think colon?

6. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
Sorry for me being unclear or vague about my question. :/

I know that it is the vertical bar and how to type it at keyboard. I also know that it means plug to, evaluated at, etc. Hmm..

My problem should be restated at "How to make the vertical bar as high as the highest object in the equation?"

(My motive for asking what is the name of the | that appears in the equation above is that I thought that | seen in keyboards is different from | used in math. (which I now know to be the same) So maybe if I use the proper |, I will solve my issue.)

Look at my example:

There, as you can see, the height of the vertical bar is smaller than that of the height of 5/x (which is the highest object in the equation). I want the vertical bar to adjust accordingly. Do you know?

Thanks!

Last edited: Feb 18, 2014
7. ### WBahn Moderator

Mar 31, 2012
20,230
5,755
So basically you have a typesetting question.

How you will do that depends entirely on the typesetting tool you are using. I see that you are using MathType, which is a program I have not used before. I use either LaTeX or Word's Equation Editor.

But my guess is that you need to do is group things the right way. Word has a grouping for a single bracket symbol which includes the pipe on the right. Thus it will automatically scale to the size of what is grouped with it. Then the entire thing can be grouped with a subscript and superscript.

I would be willing to be that MathType has something similar.

With something like LaTeX you would have more control over exactly how things looked, but it is also a lot more involved to go beyond the "default" behavior.

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8. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
Now I have a new problem:

I make the | large. But there is spacing. Maybe because the MathType assumes that the space in the numerator will be the same as the space in the denominator and vice versa.

9. ### WBahn Moderator

Mar 31, 2012
20,230
5,755
If you are wanting some horizontal space between the portion in the blue box and the vertical bar, then you should be able to do that by going into the blue boxed group and adding a space or two after the fraction (just as if the fraction was multiplied by something after it).

10. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
519
Spacing in Mathtype is provided by the second button in from the left, top row.
It is not provided by the space bar unless you have text style selected.

I cannot see why you would be using the vertical line in this situation anyway.

With differential expressions it is conventional to place them in brackets and state conditions as subscript eg

${\left( {\frac{{dy}}{{dx}}} \right)_{x = 5}}$

${\left( {\frac{{\partial \Omega }}{{\partial u}}} \right)_{v = 0}}$

As a matter of interest what setting do you use for AllAboutCircuits in Mathtype?

I use it for several sites and the setting changes for each one.

I usually use it set for "Maths and Physics Help forums".
This produces mathml tags not Tex Tags and and I manually change these for AAC to TEX

11. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
That's a definite integration problem. ...... that's why there's a vertical.

I only want the vertical bar to be just the same height as the highlighted part. but it's overflowing!!

12. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
519
In which case the limits refer to the integral not the derivative so should appear by the integral sign.

If the square brackets indicate you have already integrated from a higher derivative (which is the only reason you should be omitting the integral sign) then the limits should appear outside the second square bracket enclosing the result of the integration.

There should be not be a vertical line within the square brackets.

Lightfire likes this.
13. ### #12 Expert

Nov 30, 2010
17,895
9,314
Off topic. I think I saw this in Linux as meaning "to call a subroutine" or, "gosub", as in, "pipe the results of this [program or subroutine] into this other subroutine".

Meansquared
Comment: Find the average of three numbers and square them
Input x,y,z
gosub whatzit
end

subroutine whatzit
frog = (x+y+z)/3
return

If coded to eliminate the gosub command, you might use the command, Meansquared | frog (pronounced, meansquared pipe frog)

Please excuse the programming errors and consider the intent to explain what, "pipe" means in one programming language.

14. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
Thank you!! I'll transfer it outside!!

Any MathType users here????? Thanks!!!!