LaTeX equations can be written inline inside a sentence or placed as display equations when the expression needs more space.

Inline Equations

Write inline mathematics with single dollar signs:

The rest energy is $E=mc^2$, and the photon energy is $E=h\nu$.

Rendered result:

The rest energy is $E=mc^2$, and the photon energy is $E=h\nu$.

Display Equations

Use double dollar signs for equations that should stand alone:

$$
i\hbar \frac{\partial \psi}{\partial t}=\hat{H}\psi
$$

Rendered result:

\[i\hbar \frac{\partial \psi}{\partial t}=\hat{H}\psi\]

Aligned Derivation

For multi-line derivations, use aligned inside display math:

$$
\begin{aligned}
\hat{H}\psi
&=
\left[
-\frac{\hbar^2}{2m}\frac{d^2}{dx^2}
+\frac{1}{2}m\omega^2x^2
\right]\psi \\
&= E\psi .
\end{aligned}
$$

Rendered result:

\[\begin{aligned} \hat{H}\psi &= \left[ -\frac{\hbar^2}{2m}\frac{d^2}{dx^2} +\frac{1}{2}m\omega^2x^2 \right]\psi \\ &= E\psi . \end{aligned}\]

Mobile-Friendly Habit

Long equations can overflow on phones. Break them into aligned lines before they become too wide:

\[\begin{aligned} \Delta x\,\Delta p &\geq \frac{\hbar}{2}, \\ \Delta E\,\Delta t &\geq \frac{\hbar}{2}. \end{aligned}\]