Mathjax is what you need to **write mathematically**. If you are not already a mathematician, it takes a good time to learn how. Up to that point, you might want to use an Equation Editor that translate your writing to the symbols that Mathjax like. Use the equitation editor for the famous Euler’s formula you will get e^{i\pi } =-1. Then depending on where you want to write the formula, follow the following rule.

The in-line \(e^{i\pi } =-1\) is in line! And the displayed is in a separate line $$e^{i\pi } =-1$$.

You can also directly look at MathJax basic tutorial and quick reference and find whatever you need.