\frac{1}{\Bigl(\sqrt{\phi \sqrt{5}}-\phi\Bigr) e^{\frac25 \pi}} \equiv 1+\frac{e^{-2\pi}} {1+\frac{e^{-4\pi}} {1+\frac{e^{-6\pi}} {1+\frac{e^{-8\pi}} {1+\cdots} } } }
\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)
\displaystyle\sum_{i=1}^{k+1}i
\displaystyle= \left(\sum_{i=1}^{k}i\right) +(k+1)
\displaystyle= \frac{k(k+1)}{2}+k+1
\displaystyle= \frac{k(k+1)+2(k+1)}{2}
\displaystyle= \frac{(k+1)(k+2)}{2}
\displaystyle= \frac{(k+1)((k+1)+1)}{2}
\displaystyle1 +  \frac{q^2}{(1-q)}+\frac{q^6}{(1-q)(1-q^2)}+\cdots
= \displaystyle \prod_{j=0}^{\infty}\frac{1}{(1-q^{5j+2})(1-q^{5j+3})},
\displaystyle\text{ for }\lvert q\rvert < 1.
k_{n+1} = n^2 + k_n^2 - k_{n-1}
\Gamma\ \Delta\ \Theta\ \Lambda\ \Xi\ \Pi\ \Sigma\ \Upsilon\ \Phi\ \Psi\ \Omega
\alpha\ \beta\ \gamma\ \delta\ \epsilon\ \zeta\ \eta\ \theta\ \iota\ \kappa\ \lambda\ \mu\ \nu\ \xi
\ \omicron\ \pi\ \rho\ \sigma\ \tau\ \upsilon\ \phi\ \chi\ \psi\ \omega\ \varepsilon\ \vartheta\ \varpi\ \varrho\ \varsigma\ \varphi
\gets\ \to\ \leftarrow\ \rightarrow\ \uparrow\ \Uparrow\ \downarrow\ \Downarrow\ \updownarrow\ \Updownarrow
\Leftarrow\ \Rightarrow\ \leftrightarrow\ \Leftrightarrow\\mapsto\ \hookleftarrow
\leftharpoonup\ \leftharpoondown\ \rightleftharpoons\ \longleftarrow\ \Longleftarrow\ \longrightarrow
\Longrightarrow\ \longleftrightarrow\ \Longleftrightarrow\ \longmapsto\\hookrightarrow\ \rightharpoonup
\rightharpoondown\ \leadsto\ \nearrow\\searrow\ \swarrow\ \nwarrow
\surd\ \barwedge\ \veebar\ \odot\ \oplus\ \otimes\ \oslash\ \circledcirc\ \boxdot\\bigtriangleup
\bigtriangledown\ \dagger\ \diamond\ \star\ \triangleleft\\triangleright\ \angle\ \infty\ \prime\ \triangle
\int u \frac{dv}{dx}\,dx=uv-\int \frac{du}{dx}v\,dx
f(x) = \int_{-\infty}^\infty \hat f(\xi)\,e^{2 \pi i \xi x}
\oint \vec{F} \cdot d\vec{s}=0
\begin{aligned}\dot{x} & = \sigma(y-x) \\\dot{y} & = \rho x - y - xz \\\dot{z} & = -\beta z + xy\end{aligned}
\mathbf{V}_1 \times \mathbf{V}_2 =  \begin{vmatrix}\mathbf{i} & \mathbf{j} & \mathbf{k} \\\frac{\partial X}{\partial u} &  \frac{\partial Y}{\partial u} & 0 \\\frac{\partial X}{\partial v} &  \frac{\partial Y}{\partial v} & 0\end{vmatrix}
\hat{x}\ \vec{x}\ \ddot{x}
\left(\frac{x^2}{y^3}\right)
\left.\frac{x^3}{3}\right|_0^1
f(n) = \begin{cases} \frac{n}{2}, & \text{if } n\text{ is even} \\ 3n+1, & \text{if } n\text{ is odd} \end{cases}
\begin{aligned}\nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\\nabla \cdot \vec{\mathbf{E}} & = 4 \pi \rho \\\nabla \times \vec{\mathbf{E}}\, +\, \frac1c\, \frac{\partial\vec{\mathbf{B}}}{\partial t} & = \vec{\mathbf{0}} \\\nabla \cdot \vec{\mathbf{B}} & = 0 \end{aligned}
\begin{aligned}\nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\[1em]\nabla \cdot \vec{\mathbf{E}} & = 4 \pi \rho \\[0.5em]\nabla \times \vec{\mathbf{E}}\, +\, \frac1c\, \frac{\partial\vec{\mathbf{B}}}{\partial t} & = \vec{\mathbf{0}} \\[1em]\nabla \cdot \vec{\mathbf{B}} & = 0 \end{aligned}
\frac{n!}{k!(n-k)!} = {^n}C_k
{n \choose k}
\frac{\frac{1}{x}+\frac{1}{y}}{y-z}
\sqrt[n]{1+x+x^2+x^3+\ldots}
\begin{pmatrix}a_{11} & a_{12} & a_{13}\\a_{21} & a_{22} & a_{23}\\a_{31} & a_{32} & a_{33}\end{pmatrix}
\begin{bmatrix} 0 & \cdots & 0 \\ \vdots & \ddots & \vdots \\ 0 & \cdots & 0 \end{bmatrix}
f(x) = \sqrt{1+x} \quad (x \ge  -1)
f(x) \sim x^2 \quad (x\to\infty)
f(x) = \sqrt{1+x}, \quad x \ge -1
f(x) \sim x^2, \quad x\to\infty
\mathcal L_{\mathcal T}(\vec{\lambda})    = \sum_{(\mathbf{x},\mathbf{s})\in \mathcal T}       \log P(\mathbf{s}\mid\mathbf{x}) - \sum_{i=1}^m       \frac{\lambda_i^2}{2\sigma^2}
S (\omega)=\frac{\alpha g^2}{\omega^5} \,e ^{[-0.74\bigl\{\frac{\omega U_\omega 19.5}{g}\bigr\}^{-4}]}
f(a,b,c) = (a^2+b^2+c^2)^3