As you may have heard, Pages now supports LaTeX equations in both iOS and macOS. Even though it’s not nearly as robust as writing and typesetting LaTeX using MacTeX, it’s extremely well implemented and will be a huge convenience, especially for one-off files and shorter documents.
I like how the Equation editor in Pages provides a live preview of the equation as you type it:
As an added bonus, even though Keynote does not have the same direct LaTeX support as Pages, I found that you can copy the equation in Pages as an image and simply paste it into Keynote. The image appears to be a vector graphic because it scales perfectly without any resolution loss.
In a nutshell, this means you can also quickly add equations to Keynote via Pages on the fly.