### Author Topic: how does posting math notation work?  (Read 1803 times)

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#### Simon

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##### how does posting math notation work?
« on: October 10, 2020, 08:26:15 am »
I'd like to post a question with a math formula. I think there is a way of doing it but see no instructions.
« Last Edit: October 10, 2020, 09:15:14 am by Simon »

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#### IanB

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##### Re: how does posting math notation work?
« Reply #1 on: October 10, 2020, 08:33:13 am »
Go to MathJax sandbox to get your syntax right, for example like this: http://jbergknoff.github.io/mathjax-sandbox/#JCRjPVxzcXJ0e2FeMitiXjJ9JCQ%3D

Then paste the formula into your post surrounded by double dollar signs:
$$c=\sqrt{a^2+b^2}$$
The reason for using the sandbox is that preview doesn't work in the editor here, so you need to use an external tool to see what your formulas will look like before posting.
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#### Simon

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##### Re: how does posting math notation work?
« Reply #2 on: October 10, 2020, 08:34:25 am »
Thank you.

#### Simon

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##### Re: how does posting math notation work?
« Reply #3 on: October 10, 2020, 08:35:24 am »
But is there a list of notation codes somewhere? as it is I use two programs with different methods of doing the same thing, I am sure this will be a third.

#### IanB

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##### Re: how does posting math notation work?
« Reply #4 on: October 10, 2020, 08:38:57 am »
It's basically LaTeX math notation. I usually Google that to find tutorials and crib sheets.
« Last Edit: October 10, 2020, 08:45:41 am by IanB »
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#### Simon

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##### Re: how does posting math notation work?
« Reply #5 on: October 10, 2020, 08:41:31 am »
Ah OK, now I know what to google: https://oeis.org/wiki/List_of_LaTeX_mathematical_symbols It's certainly not responding to the keywords that open office uses.

#### IanB

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##### Re: how does posting math notation work?
« Reply #6 on: October 10, 2020, 08:45:01 am »
This seems to be a good reference:

https://en.wikibooks.org/wiki/LaTeX/Mathematics
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#### Simon

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##### Re: how does posting math notation work?
« Reply #7 on: October 10, 2020, 08:48:02 am »
It's the long fraction line that seems to be missing, i think I have to use an over line on the denominator

No it's a \frac:

$$\frac {3-2s} {s^2-4s+9}$$

#### IanB

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##### Re: how does posting math notation work?
« Reply #8 on: October 10, 2020, 09:09:22 am »
You can do it either way. For example, this will work too:
Code: [Select]
{3-2s}\over{s^2-4s+9}$${3-2s}\over{s^2-4s+9}$$
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#### Simon

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##### Re: how does posting math notation work?
« Reply #9 on: October 10, 2020, 09:11:03 am »
Ah, that is what I was hoping but did not see it. in Libre office you just write "over"

#### Ian.M

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##### Re: how does posting math notation work?
« Reply #10 on: October 10, 2020, 10:50:29 am »
Mathjax 2.7 documentation: http://docs.mathjax.org/en/v2.7-latest/
The original thread where Dave decided to enable Mathjax: https://www.eevblog.com/forum/suggestions/latex-for-eevblog/

#### Doctorandus_P

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##### Re: how does posting math notation work?
« Reply #11 on: October 12, 2020, 11:31:39 am »
Write it on a piece of paper.
Make a picture of it.
Post it.

#### mathsquid

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##### Re: how does posting math notation work?
« Reply #12 on: October 13, 2020, 02:41:19 am »
So just put latex code in here and it works?

$$\sum_{n=1}^\infty \frac{1}{n^2} = \frac{\pi^2}{6}$$

Edit: Sweet.

#### dnwheeler

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##### Re: how does posting math notation work?
« Reply #13 on: October 13, 2020, 09:50:08 pm »
\over and \frac are not equivalent. There is even a visible difference in the examples above.

#### IanB

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##### Re: how does posting math notation work?
« Reply #14 on: October 14, 2020, 02:58:53 pm »
\over and \frac are not equivalent. There is even a visible difference in the examples above.

Using \frac:

$$\frac{3-2s}{s^2-4s+9}$$

Using \over:

$${3-2s}\over{s^2-4s+9}$$

I don't see any difference. How are they different?
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#### dnwheeler

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##### Re: how does posting math notation work?
« Reply #15 on: October 14, 2020, 08:31:54 pm »
Interesting. It appears to be some sort of rendering issue. In the previous posts, the "frac" line is clearly 1 pixel higher than the "over" line. In your post, they look the same, but as I'm typing this, the copy of your message shown below the editor shows the "over" line 1 pixel higher.

FWIW, I see the same behavior on the Chromium version of Edge and with Chrome (on a Windows 10 system).

There are other technical differences discussed here: https://tex.stackexchange.com/questions/73822/what-is-the-difference-between-over-and-frac

#### IanB

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##### Re: how does posting math notation work?
« Reply #16 on: October 14, 2020, 09:22:40 pm »
So it's a case of \over being a TeX primitive whereas \frac is a LaTeX macro with more robust behavior?

However, I am with Knuth who apparently said that \over is a more natural syntax for mathematicians. As long as I see \over rendering properly it is the one I would prefer to use. I find \frac more awkward as it doesn't support a linear thought process when writing equations.

Edit: apparently \frac also uses a form of \over internally when it expands the macro.
« Last Edit: October 14, 2020, 09:25:16 pm by IanB »
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#### RoGeorge

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##### Re: how does posting math notation work?
« Reply #17 on: October 14, 2020, 09:35:25 pm »
Enclose the formula between backslash dollar if you need an inline formula, for example like this one $\Phi = BA$, placed in a normal conversation.

Sometimes I use https://www.codecogs.com/latex/eqneditor.php as an online editor, good to see the rendered formula, because the forum shows the rendered formula only after posting, it does not render it at preview.

LATER EDIT:  Found an older post with a clean example in it.

Latex enclosed by backslash dollar will render it inline, when enclosed by double dollar will render centered, on a new line.

Example:
Code: [Select]
From Faraday's induction law, the induced voltage $V$ in an $N$ turns coil will be:$$V = -N\frac{\vartriangle \Phi}{\vartriangle t}$$where $\Phi$ is the magnetic flux
From Faraday's induction law, the induced voltage $V$ in an $N$ turns coil will be:

$$V = -N\frac{\vartriangle \Phi}{\vartriangle t}$$
where $\Phi$ is the magnetic flux

The Latex render will be seen only after posting the message, not at preview.
« Last Edit: October 14, 2020, 09:44:57 pm by RoGeorge »

#### RoGeorge

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##### Re: how does posting math notation work?
« Reply #18 on: October 14, 2020, 09:57:31 pm »
Code: [Select]
Trying a new one$\vartheta=2\pi \tag{5.5} \label{eq:best}$Space between consecutive formulae $\mathbf{A}\textbf{B} \tag{5.6} \label{eq:special}$A reference to eq. \eqref{eq:best} and a cross-reference to \eqref{eq:special}.
Trying a new one
$\vartheta=2\pi \tag{5.5} \label{eq:best}$
Space between consecutive formulae
$\mathbf{A}\textbf{B} \tag{5.6} \label{eq:special}$
A reference to eq. \eqref{eq:best} and a cross-reference to \eqref{eq:special}.

« Last Edit: October 14, 2020, 10:38:27 pm by RoGeorge »

#### Andy Watson

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##### Re: how does posting math notation work?
« Reply #19 on: October 14, 2020, 10:35:53 pm »
And can I reference a previous post. Like equation \eqref{eq:best} ?

Apparently I can !
« Last Edit: October 14, 2020, 10:37:25 pm by Andy Watson »

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#### wizard69

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##### Re: how does posting math notation work?
« Reply #20 on: October 16, 2020, 04:45:22 am »
Interesting thread as i never considered math posting here.    Sadly this doesn't work on an Iphone with MathML turned on.   Not sure what is going on there but it works fine on Firefox on Linux

#### Cerebus

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##### Re: how does posting math notation work?
« Reply #21 on: October 18, 2020, 11:31:22 pm »
Interesting thread as i never considered math posting here.    Sadly this doesn't work on an Iphone with MathML turned on.   Not sure what is going on there but it works fine on Firefox on Linux

Yeah, it does, it's just that the site is noticing you're on a phone and serving a 'phone' version of the site. Go to the bottom of the page, select 'menu' and then 'full site'.
Anybody got a syringe I can use to squeeze the magic smoke back into this?

Smf