$$
\lim_{n \to \infty}
\sum_{k=1}^n \frac{1}{k^2}
= \frac{\pi^2}{6} \qquad {for,all\quad }x\in \mathbb{R} $$

$\heartsuit$

$$\sqrt[3]
{2+3}$$

$$\underbrace{a+b+\cdots+z}_{26}$$

$$\widehat{adfdsfsaf}$$
$$\hat{x}\overline{x}$$
$$[\overline{x} - \frac{1.96s}{\sqrt{T}}]$$

$$y’’’’’’ = 4 \csc\sinh \inf \ \liminf_{x \rightarrow 0} \liminf$$
$$x^{1/2} \frac{yy}{xx} \binom{n}{k}C^m_k $$
$$\mathrm{C}^m_k $$

$$\sum_{n=0}^k \prod_{i=1}^n$$

$$x{\Big{\frac{\frac{1}{2}}{x}\Big}y}^3$$

$$\left| \begin{array}{}
x_{11} & x_{12} & \ldots \
x_{21} & x_{22} & \ldots \
\vdots & \vdots & \ddots
\end{array} \right|$$

$$\displaystyle ddd\scriptstyle ttt\scriptscriptstyle aa$$

$$\times \leq \geq > < \sim \subset \subseteq \supset \in \notin \Leftrightarrow \pm \div \approx \cdot$$

$$T(n) = \left{ \begin{array}{ll}
\Theta(1) \
2T(\frac{n}{2}) + \Theta(n)
\end{array} \right.
$$

$$\begin{array}
yy = \left{ \begin{array}{ll}
a & \textrm{if $d>c$}\
b+x & \textrm{in the morning}\
l & \textrm{all day long}
\end{array} \right.
\end{array}$$