#шпаргалки

$\alpha$ - @a 
$\beta$ - @b 
$\gamma$ - @g $\Gamma$ - @G 
$\delta$ - @d $\Delta$ - @D
$\zeta$ -@z
$\sigma$ - @s $\Sigma$ - @S
$\kappa$ - @k 
$\lambda$ - @l $\Lambda$ - @L
$\epsilon$ - @e $\varepsilon$ - :e
$\theta$ - @t $\Theta$ - @T $\vartheta$ - :t
$\upsilon$ - @u
$\iota$ - @i 
$\omega$ - @o; ome $\Omega$ - @O; Ome 

$_\text{smol}$ - sts
$x^{2}$ - sr
$x^{3}$ - cb
$x^{y}$ - rd
$x_{1}$ = _
$\sqrt{ x }$ - sq
$\frac{x}{y}$ - //
$e^{ x }$ - ee
$x^{-1}$ - invs
$x^{*}$ - conj
$\mathrm{Re}$ - Re
$\mathrm{Im}$ - Im
$\mathbf{letter}$ - bf
$\mathrm{letter}$ - rm
$\mathrm{Tr}$ - trace

$\hat{x}$ - hat
$\bar{x}$ - bar
$\dot{x}$ - dot
$\ddot{x}$ - ddot
$x\cdot x$ - cdot
$\tilde{x}$ - tilde
$\underline{x}$ - und
$\vec{x}$ - vec
$\infty$ - ooo
$\sum$ - sum
$\prod$ - prod
$$
\sum_{i=1}^{N} 
$$ sum+Tab
$$
\prod_{i=1}^{N} 
$$ prod+Tab
$\lim_{ n \to \infty }$ - lim
$\pm$ - +-
$\mp$ - -+
$\dots$ - ...
$\nabla$ - nabl; del
$\times$ - xx
$\cdot$ - **
$\parallel$ - para
$\equiv$ - ===
$\neq$ - !=
$\geq$ - >=
$\leq$ - <=
$\gg$ - >>
$\ll$ - <<
$\sim$ - simm
$\simeq$ - sim=
$\propto$ - prop
$\leftrightarrow$ - <->
$\to$ - ->
$\mapsto$ - !>
$\implies$ = =>
$\impliedby$ - =<
$\iff$ - iff
$\cap$ - and
$\cup$ - orr
$\in$ - inn
$\not\in$ - notin
$\subseteq$ - sub=
$\supseteq$ - sup=
$\emptyset$ - eset
$\{ x \}$ - set
$\exists$ - exists 

$\mathcal{L}$ - LL
$\mathcal{H}$ - HH
$\mathbb{C}$ - CC
$\mathbb{R}$ - RR
$\mathbb{Q}$ - QQ
$\mathbb{Z}$ - ZZ

$\frac{ \partial y }{ \partial x }$ - par
$\frac{d}{dt}$ - ddt
$\int x \, dx$ - int+Tab
$\int_{0}^{1}  \, dx$ - dint
$\oint$ - oint
$\iint$ - iint
$\iiint$ - iiint
$\int_{0}^{\infty} x \, dx$ - oinf
$\int_{-\infty}^{\infty} x \, dx$ - infi

$$
\begin{matrix}
a_{1} & a_{2} & a_{3} \\
b_{1} &  & b_{3} \\
\dots & \dots & \dots \\
 & x_{2} & x_{3}
\end{matrix}
$$
matrix (Tab for column, Enter for row)
$\begin{pmatrix}x_{1} & x_{2} \\ x_{3} & x_{4}\end{pmatrix}$ - pmat
$\begin{bmatrix}x_{1} & x_{2} \\ x_{3} & x_{4}\end{bmatrix}$ - bmat
$\begin{Bmatrix}x_{1} & x_{2} \\ x_{3} & x_{4}\end{Bmatrix}$ - Bmat
$\begin{vmatrix}x_{1} & x_{2} \\ x_{3} & x_{4}\end{vmatrix}$ - vmat
$\begin{Vmatrix}x_{1} & x_{2} \\ x_{3} & x_{4}\end{Vmatrix}$ - Vmat
$$
\begin{cases}
function_{1} \\
function_{2} \\
function_{3}
\end{cases}
$$ cases
$$
\begin{array}
x_{1} & x_{2} & x_{3} \\
two \\
three
\end{array}
$$ array
$$
\begin{align}
x_{1}   & & x_{2}  & & x_{3} \\
y_{1} &  & y_{2} &  & y_{3}
\end{align}
$$ align 
(for structuring content)

$\langle x \rangle$ - avg
$\lvert x \rvert$ - norm
$\lVert x \rVert$ - Norm
$\lceil x_{1}x_{2} \rceil$ - ceil
$\lfloor x_{1}x_{2} \rfloor$ - floor
$|x_{1}x_{2}|$ - mod
$\left( x_{1}x_{2} \right)$ - lr(; lr{; lr[
$\left< x \right>$ - lra