### The Cauchy-Schwarz Inequality (TeX)

\[ \left( \sum_{k=1}^n a_k b_k \right)^2 \leq \left( \sum_{k=1}^n a_k^2 \right) \left( \sum_{k=1}^n b_k^2 \right) \]
### Standard Deviation (MathML)

$$\sigma =\sqrt{\frac{1}{N}{\displaystyle \sum _{i=1}^{N}{({x}_{i}-\mu )}^{2}}}.$$
### Inline equation (TeX)

Finally, while display equations look good for a page of samples, the ability to mix math and text in a paragraph is also important. This expression \(\sqrt{3x-1}+(1+x)^2\) is an example of an inline equation. As you see, MathJax equations can be used this way as well, without unduly disturbing the spacing between lines.