Math equations #

Math Fonts #

Ref: Mathematical fonts - Overleaf, Online LaTeX Editor

Bold: $\mathbf{RQSZN}$ , $\mathbf{1}$ , $\boldsymbol{\beta}$

\mathbf{X}
\mathbf{1}
\boldsymbol{\beta}    % requires amsbsy package % https://tex.stackexchange.com/a/99286

Bold hollow: $\mathbb{RQSZN}$ (for numbers extra packages are needed)

\mathbb{R}

Cursive: $\mathcal{RQSZN}$

\mathcal{N}

Force Non-Display Size #

Compare:

$$ \textstyle{\sum}_{i=1}^{10} i $$

$$ \sum_{i=1}^{10} i $$

\textstyle{\sum}_{i=1}^{10}

\sum_{i=1}^{10}

Combining Symbols #

Above: $x\overset{!}{=}0$

x\overset{!}{=}0

With negative space: $\mkern12mu\not\mkern-24mu\iff$ (credit; another way not supported by KaTeX)

% The first part is for stopping eating into contents before
\mkern12mu\not\mkern-24mu\iff

% or
\usepackage{centernot}
\centernot\iff

Better `\bar` #

Ref: stacking symbols - The \bar and \overline commands - TeX - LaTeX Stack Exchange

Gives the middle one:

\usepackage{amsfonts}
\newcommand{\overbar}[1]{\mkern 1.5mu\overline{\mkern-1.5mu#1\mkern-1.5mu}\mkern 1.5mu}

$\overbar{\mathbb{R}}$

Alignment #

Basic aligns & tag position #

Single line equation #

Using \label{eq1} in any expression, and refer to it as eq1; $\eqref{eq1}$ ; $\ref{eq1}$ later

…by typing:

[eq1](#eq1)
$\eqref{eq1}$
$\ref{eq1}$

The latter two are valid in LaTeX as well.

This requires adding macros when importing KaTeX. See Issue #2003 · KaTeX/KaTeX for details.

There is also \htmlId functionality which is less intuitive to use but do not require adding macros.

Auto tag: (Numbers are continuous during the whole webpage)

$$\begin{equation} x = y \label{eq1} \end{equation} $$

\begin{equation}
  x = y \label{eq1}
\end{equation}

Manual tag: (Numbers are not continuous)

$$x = y \tag{1.1}$$

x = y \tag{1.1}

% or

\begin{equation*}
  x = y \tag{1.1}
\end{equation*}

No tag:

$$\begin{equation*} x = y \end{equation*}$$

x = y

% or

\begin{equation*}
  x = y
\end{equation*}

Multi-line signle equation with `aligned` #

Auto tag:

$$ \begin{equation} \begin{aligned} x &= y \\ &= z \end{aligned} \end{equation} $$

\begin{equation}
\begin{aligned}
  x &= y \\
  &= z
\end{aligned}
\end{equation}

Manual tag: (For no tag, remove the \tag command.)

$$ \begin{aligned} x &= y \\ &= z \tag{2.1} \end{aligned} $$

\begin{aligned}
  x &= y \\
  &= z \tag{2.1}
  \end{aligned}

Multiple equations with `Align` #

Auto tag:

$$ \begin{align} x &= y \\ 2x &= 2z \end{align} $$

\begin{align}
  x &= y \\
  2x &= 2z
\end{align}

No tag: (For manual tag, add \tag command.)

$$ \begin{align*} x &= y \\ 2x &= 2z \end{align*} $$

\begin{align*}
  x &= y \\
  2x &= 2z
\end{align*}

More examples #

Cases:

$$ \begin{cases} x=1 & y=1\\ x=2 & y=2 \end{cases} $$

\begin{cases}
  x=1 & y=1\\
  x=2 & y=2
\end{cases}

Symbols as equation tag: (Ref)

$$E=mc^2 \tag{$*$}$$

E=mc^2 \tag{$*$}

Spaces in equations:

$$ \begin{aligned} x &= 12345 \\ &\phantom{\ggg} + 67890 \end{aligned} $$

\begin{aligned}
  x &= 12345 \\
  &\phantom{\ggg} + 67890
\end{aligned}

Braces with multiple lines:

$$ \underbrace{abcdef}_{ \begin{subarray}{l} \text{hello}\\ \text{world} \end{subarray} } $$

\underbrace{abcdef}_{
  \begin{subarray}{l}
    \text{hello}\\
    \text{world}
  \end{subarray}
}

Horizontally aligned braces: (Ref)

$$ f(x,z) = \underbrace{\int^a_b x\ dx}_{\text{Things}} +\underbrace{\vphantom{\int_b}2333z}_{\text{More things}} $$

f(x,z) =
\underbrace{\int^a_b x\ dx}_{\text{Things}}
+\underbrace{\vphantom{\int_b}2333z}_{\text{More things}}

More horizontally aligned braces: (Ref)

$$ f(x,z) = \underbrace{\int^a_b x\ dx}_{\text{Things}} +\overbrace{\vphantom{\int^a}42xz^2}^{\mathclap{\text{Longer other things}}} +\underbrace{\vphantom{\int_b}2333z}_{\mathclap{\text{More longer things}}} $$

f(x,z) =
\underbrace{\int^a_b x\ dx}_{\text{Things}} 
+\overbrace{\vphantom{\int^a}42xz^2}^{\mathclap{\text{Longer other things}}}
+\underbrace{\vphantom{\int_b}2333z}_{\mathclap{\text{More longer things}}}

Newer and better environment defaults #

Space in braces #

Refs:

\usepackage{amsmath}
\makeatletter
\def\env@cases{%
  \let\@ifnextchar\new@ifnextchar
  \left\lbrace
  \def\arraystretch{1.1}%
  \array{@{\,}l@{\quad}l@{}}%
}
\makeatother