EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: Simon 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.

Go to MathJax sandbox to get your syntax right, for example like this: http://jbergknoff.github.io/mathjaxsandbox/#JCRjPVxzcXJ0e2FeMitiXjJ9JCQ%3D (http://jbergknoff.github.io/mathjaxsandbox/#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.

Thank you.

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.

It's basically LaTeX math notation. I usually Google that to find tutorials and crib sheets.

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.

This seems to be a good reference:
https://en.wikibooks.org/wiki/LaTeX/Mathematics

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:
$$ \frac {32s} {s^24s+9}$$

You can do it either way. For example, this will work too:
{32s}\over{s^24s+9}
$${32s}\over{s^24s+9}$$

Ah, that is what I was hoping but did not see it. in Libre office you just write "over"

Mathjax 2.7 documentation: http://docs.mathjax.org/en/v2.7latest/ (http://docs.mathjax.org/en/v2.7latest/)
The original thread where Dave decided to enable Mathjax: https://www.eevblog.com/forum/suggestions/latexforeevblog/ (https://www.eevblog.com/forum/suggestions/latexforeevblog/)

Write it on a piece of paper.
Make a picture of it.
Post it.

So just put latex code in here and it works?
$$\sum_{n=1}^\infty \frac{1}{n^2} = \frac{\pi^2}{6}$$
Edit: Sweet.

\over and \frac are not equivalent. There is even a visible difference in the examples above.

\over and \frac are not equivalent. There is even a visible difference in the examples above.
Using \frac:
$$\frac{32s}{s^24s+9}$$
Using \over:
$${32s}\over{s^24s+9}$$
I don't see any difference. How are they different?

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/whatisthedifferencebetweenoverandfrac (https://tex.stackexchange.com/questions/73822/whatisthedifferencebetweenoverandfrac)

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.

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 (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:
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.

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 crossreference 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 crossreference to \eqref{eq:special}.

And can I reference a previous post. Like equation \eqref{eq:best} ?
Apparently I can !

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

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'.

of course you can just do a screen shot and stick it in as an image

of course you can just do a screen shot and stick it in as an image
I can see how that would appeal to someone for whom full stops and starting a sentence with a capital letter seems too onerous. >:D

I normally use the equation editor in Microsoft Word to generate equations to be included in Word documents.
Is there a simple way to include such an equation into a post here?

I normally use the equation editor in Microsoft Word to generate equations to be included in Word documents.
Is there a simple way to include such an equation into a post here?
See here (https://officewatch.com/2017/mathsequationlateximprovementsword2016/) for details of Word's \$\LaTeX\$ math mode capabilities in the equation editor. There's an embedded video on how to get \$\LaTeX\$ out of the equation editor.