latex

What this skill does

# LaTeX Skill

## 1. Overview

LaTeX is a markup language and typesetting system for producing high-quality documents. It excels at structured documents with complex formatting, mathematics, cross-references, and bibliographies.

**When to use LaTeX:**
- Academic papers, journal submissions
- Theses and dissertations
- Technical documentation
- CVs and résumés
- Presentations (Beamer)
- Books, reports, letters

**Key concepts:**

| Concept | Description |
|---------|-------------|
| **Preamble** | Everything before `\begin{document}` — class, packages, settings |
| **Document body** | Content between `\begin{document}` and `\end{document}` |
| **Commands** | Start with `\`, e.g. `\textbf{bold}`. Optional args in `[]`, required in `{}` |
| **Environments** | `\begin{name}...\end{name}` blocks for scoped formatting |
| **Packages** | Extensions loaded with `\usepackage{name}` in the preamble |

## 2. Document Structure

### Document Classes

```latex
\documentclass[options]{class}
```

| Class | Use case |
|-------|----------|
| `article` | Short documents, papers, assignments |
| `report` | Longer documents with chapters |
| `book` | Books (front/back matter, chapters) |
| `beamer` | Presentations/slides |
| `letter` | Formal letters |
| `memoir` | Flexible — replaces article/report/book |

### Common Class Options

```latex
\documentclass[12pt,a4paper,twocolumn,draft]{article}
```

| Option | Values |
|--------|--------|
| Font size | `10pt`, `11pt`, `12pt` |
| Paper | `a4paper`, `letterpaper`, `a5paper` |
| Columns | `onecolumn`, `twocolumn` |
| Sides | `oneside`, `twoside` |
| Draft | `draft` (shows overfull boxes, skips images) |

### Minimal Document

```latex
\documentclass[12pt,a4paper]{article}

% === PREAMBLE ===
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amsmath, amssymb}
\usepackage{graphicx}
\usepackage{hyperref}

\title{My Document}
\author{Author Name}
\date{\today}

% === BODY ===
\begin{document}
\maketitle
\tableofcontents

\section{Introduction}
Content here.

\end{document}
```

## 3. Text Formatting

### Style Commands

| Command | Result |
|---------|--------|
| `\textbf{text}` | **bold** |
| `\textit{text}` | *italic* |
| `\underline{text}` | underlined |
| `\emph{text}` | emphasis (italic, or upright if already italic) |
| `\texttt{text}` | `monospace` |
| `\textsc{text}` | SMALL CAPS |
| `\textsf{text}` | sans-serif |

### Font Sizes

Smallest to largest:
```
\tiny  \scriptsize  \footnotesize  \small  \normalsize
\large  \Large  \LARGE  \huge  \Huge
```

Use as: `{\large This text is large.}` or as environment.

### Font Families

| Command | Declaration | Family |
|---------|-------------|--------|
| `\textrm{}` | `\rmfamily` | Serif (Roman) |
| `\textsf{}` | `\sffamily` | Sans-serif |
| `\texttt{}` | `\ttfamily` | Monospace |

### Alignment

```latex
\begin{center}    Centered text.    \end{center}
\begin{flushleft} Left-aligned.     \end{flushleft}
\begin{flushright} Right-aligned.   \end{flushright}
```

Or inline: `\centering`, `\raggedright`, `\raggedleft`

### Spacing

```latex
\vspace{1cm}          % vertical space
\hspace{2em}          % horizontal space
\vfill                % stretch vertical
\hfill                % stretch horizontal
\\[0.5cm]             % line break with extra space
\setlength{\parskip}{0.5em}   % paragraph spacing
\setlength{\parindent}{0pt}   % remove paragraph indent
\noindent             % suppress indent for one paragraph
```

Line spacing (requires `setspace` package):
```latex
\usepackage{setspace}
\onehalfspacing    % or \doublespacing, \singlespacing
```

### Special Characters

These characters must be escaped:

| Character | LaTeX | Character | LaTeX |
|-----------|-------|-----------|-------|
| `%` | `\%` | `$` | `\$` |
| `&` | `\&` | `#` | `\#` |
| `_` | `\_` | `{` | `\{` |
| `}` | `\}` | `~` | `\textasciitilde` |
| `^` | `\textasciicircum` | `\` | `\textbackslash` |

## 4. Document Organization

### Sectioning

```latex
\part{Part Title}           % only in report/book
\chapter{Chapter Title}     % only in report/book
\section{Section}
\subsection{Subsection}
\subsubsection{Subsubsection}
\paragraph{Paragraph}
\paragraphsub{Subparagraph}
```

Starred versions (`\section*{}`) suppress numbering and TOC entry.

### Table of Contents

```latex
\tableofcontents    % requires two compilations
\listoffigures
\listoftables
```

### Lists

```latex
% Bulleted
\begin{itemize}
  \item First item
  \item Second item
\end{itemize}

% Numbered
\begin{enumerate}
  \item First
  \item Second
\end{enumerate}

% Labeled
\begin{description}
  \item[Term] Definition here.
\end{description}
```

Customize with `enumitem` package:
```latex
\usepackage{enumitem}
\begin{enumerate}[label=(\alph*), start=1]
```

### Cross-References

```latex
\section{Methods}\label{sec:methods}
See Section~\ref{sec:methods} on page~\pageref{sec:methods}.
```

With `hyperref`, use `\autoref{sec:methods}` for automatic "Section 2" text.

**Rule:** Always place `\label` *after* `\caption` (in floats) or after the sectioning command.

### Footnotes

```latex
This has a footnote.\footnote{Footnote text here.}
```

## 5. Mathematics

### Inline vs Display

```latex
Inline: $E = mc^2$ or \(E = mc^2\)

Display:
\[ E = mc^2 \]

% Numbered equation:
\begin{equation}\label{eq:einstein}
  E = mc^2
\end{equation}
```

### Essential Packages

```latex
\usepackage{amsmath}    % align, cases, matrices, etc.
\usepackage{amssymb}    % extra symbols (ℝ, ℤ, etc.)
\usepackage{mathtools}  % extends amsmath (dcases, coloneqq, etc.)
```

### Common Constructs

```latex
% Fractions
\frac{a}{b}          \dfrac{a}{b}  (display-size)

% Roots
\sqrt{x}             \sqrt[3]{x}

% Sub/superscripts
x_{i}   x^{2}   x_{i}^{2}   a_{i,j}

% Sums, products, integrals
\sum_{i=1}^{n} x_i      \prod_{i=1}^{n} x_i
\int_{0}^{\infty} f(x)\,dx
\lim_{x \to \infty} f(x)

% Brackets (auto-sized)
\left( \frac{a}{b} \right)
\left[ ... \right]
\left\{ ... \right\}
```

### Matrices

```latex
\begin{pmatrix} a & b \\ c & d \end{pmatrix}   % (a b; c d)
\begin{bmatrix} a & b \\ c & d \end{bmatrix}   % [a b; c d]
\begin{vmatrix} a & b \\ c & d \end{vmatrix}   % |a b; c d| (determinant)
\begin{Bmatrix} a & b \\ c & d \end{Bmatrix}   % {a b; c d}
```

### Aligned Equations

```latex
\begin{align}
  f(x) &= x^2 + 2x + 1 \label{eq:f} \\
  g(x) &= x^3 - 1       \label{eq:g}
\end{align}

% No numbering:
\begin{align*}
  a &= b + c \\
  d &= e + f
\end{align*}
```

### Cases

```latex
f(x) = \begin{cases}
  x^2  & \text{if } x \geq 0 \\
  -x^2 & \text{if } x < 0
\end{cases}
```

### Greek Letters

| Lower | Command | Upper | Command |
|-------|---------|-------|---------|
| α | `\alpha` | Α | `A` |
| β | `\beta` | Β | `B` |
| γ | `\gamma` | Γ | `\Gamma` |
| δ | `\delta` | Δ | `\Delta` |
| ε | `\epsilon`, `\varepsilon` | Ε | `E` |
| θ | `\theta` | Θ | `\Theta` |
| λ | `\lambda` | Λ | `\Lambda` |
| μ | `\mu` | — | — |
| π | `\pi` | Π | `\Pi` |
| σ | `\sigma` | Σ | `\Sigma` |
| φ | `\phi`, `\varphi` | Φ | `\Phi` |
| ω | `\omega` | Ω | `\Omega` |

### Common Math Symbols

| Symbol | Command | Symbol | Command |
|--------|---------|--------|---------|
| ≤ | `\leq` | ≥ | `\geq` |
| ≠ | `\neq` | ≈ | `\approx` |
| ± | `\pm` | × | `\times` |
| ÷ | `\div` | · | `\cdot` |
| ∈ | `\in` | ∉ | `\notin` |
| ⊂ | `\subset` | ⊆ | `\subseteq` |
| ∪ | `\cup` | ∩ | `\cap` |
| ∞ | `\infty` | ∂ | `\partial` |
| ∇ | `\nabla` | ∀ | `\forall` |
| ∃ | `\exists` | → | `\to`, `\rightarrow` |
| ⇒ | `\Rightarrow` | ⇔ | `\Leftrightarrow` |
| ℝ | `\mathbb{R}` | ℤ | `\mathbb{Z}` |
| … | `\dots`, `\ldots`, `\cdots` | | |

## 6. Tables

### Basic Table

```latex
\begin{table}[htbp]
  \centering
  \caption{Results summary}\label{tab:results}
  \begin{tabular}{lcrp{4cm}}
    \toprule
    Name & Count & Score & Description \\
    \midrule
    Alpha & 10 & 95.2 & First entry \\
    Beta  & 20 & 87.1 & Second entry \\
    \bottomrule
  \end{tabular}
\end{table}
```

### Column Specifiers

| Spec | Al