Inline forms: $a + b$ and \(c + d\) within text.

Display forms:
$$ e = mc^2 $$
\[ \int_0^1 x \, dx \]

\begin{equation}
  f(x) = x^2 \tag{$\star$}
\end{equation}

\begin{gather}
  a = b \\
  c = d
\end{gather}
