# What formula markup is this?

Here's a web page from 2013 using some variant of TeX-style formula markup. Modern Chrome and Firefox no longer render the formula syntax on this page. Excerpt:

$$P(text{CTR}_A,text{CTR}_B|text{data})$$ is a two-dimensional function of $$text{CTR}_A$$ and $$text{CTR}_B.$$  So to find $$P(text{CTR}_A>text{CTR}_B|text{data})$$ we have to add up all the probabilities in the region where $$text{CTR}_A>text{CTR}_B$$:

$$!P(text{CTR}_A > text{CTR}_B|text{data}) = iintlimits_{text{CTR}_A > text{CTR}_B} P(text{CTR}_A,text{CTR}_B|text{data}) dtext{CTR}_A dtext{CTR}_B.$$

To actually calculate this integral will require a few insights.  The first is that for many standard $$A/B$$ tests, $$A$$ and $$B$$ are independent because they are observed by non-overlapping populations.  Keeping this in mind, we have:

$$!P(text{CTR}_A,text{CTR}_B|text{data}) = P(text{CTR}_A|text{data}) P(text{CTR}_B|text{data}).$$


Questions:

1. What library / technology was meant to interpret this markup?
2. Is there an easy way to render these formulas today? Maybe I could save the HTML from these pages and run it through some renderer? Or maybe there's an online interpreter?
• Chrome and Firefox have never been able to natively render these. The code quoted is also very wrong as all \ are missing. Web pages will need javascript libraries like mathjax or katex to be loaded on the page in order for them to render this in a browser. Both of which are off topic here. Commented Oct 23, 2020 at 6:09
• I would guess that it was mathjax (or jsmath, its predecessor) but an update to the blog software has stripped all the \  making it unusable Commented Oct 23, 2020 at 9:41
• Both comments are right. I will gladly accept either one as an answer. Commented Oct 27, 2020 at 21:51