I am able to render mathjax in posts but have had to do that by enclosing the code in two dollar signs which puts the equations on a new line by themselves such as $$x\cos(\omega t)$$ Elsewhere I have also been able to render equations in line by using single dollar signs but that doesn’t appear to work here. Does anyone know if there is a way to render equations inline

Hi Dan!
From: https://www.dsprelated.com/thread/1114/forums-upda...
2- If you want your equation to be displayed inline, use:
\( e^{i\pi}+1=0 \)
\( e^{i\pi}+1=0 \)

Also would like to recommend the MathJax / KaTeX sandbox pages; it's a lot easier to develop equations in real-time there, and add here.
KaTeX: https://katex.org/
MathJax: https://jbergknoff.github.io/mathjax-sandbox/
The KaTeX sandbox is live-update, but KaTeX isn't 100% compatible with MathJax. (Generally if you can get something to work with KaTeX it will work with MathJax, but not necessarily the other way around.)
\begin{aligned}\int_{-\infty}^\infty\int_{-\infty}^\infty e^{-(x^2+y^2)} dx\, dy &=\int_0^\infty\int_0^{2\pi} e^{-r^2} r\, dr\, d\theta \\ &= 2\pi \int_0^\infty e^{-r^2} r\, dr \\ &= -\pi \left[ e^{-r^2} \right]_0^\infty \\ &= \pi \end{aligned}
Bizarre... why does it render when there is no $ or \[ ?
OK, also it has to be on one paragraph in the forum posts; can't span more than one paragraph. (use shift+Enter instead of Enter for a linebreak)
\begin{aligned}
\int_{-\infty}^\infty\int_{-\infty}^\infty e^{-(x^2+y^2)} dx\, dy &=\int_0^\infty\int_0^{2\pi} e^{-r^2} r\, dr\, d\theta \\
&= 2\pi \int_0^\infty e^{-r^2} r\, dr \\
&= -\pi \left[ e^{-r^2} \right]_0^\infty \\
&= \pi
\end{aligned}
source:
\begin{aligned}
\int_{-\infty}^\infty\int_{-\infty}^\infty e^{-(x^2+y^2)} dx\, dy
&=\int_0^\infty\int_0^{2\pi} e^{-r^2} r\, dr\, d\theta \\
&= 2\pi \int_0^\infty e^{-r^2} r\, dr \\
&= -\pi \left[ e^{-r^2} \right]_0^\infty \\
&= \pi \end{aligned}

I think single dollar signs worked for me in the past. $ a = 6*b + 2$ The quick brown fox jumps over the lazy dog. But it doesn't seem to work now, as you said. Stephane, can you help?