Examples: $\varphi_i$, \(\dfrac12\), \[\sum_{n=1}^\infty x^n\], etc
$\varphi_i$
\(\dfrac12\)
\[\sum_{n=1}^\infty x^n\]
\[ \zeta(s) = \sum_{n=1}^\infty\frac{1}{n^s} \]