# Using braces to label parts of an equation

Given an equation, say Bayes' rule,

``````\$P(X \mid O) \propto P(X)P(O \mid X)\$
``````

how do I label the different parts of the equation using curly braces?

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I think you're after the `\underbrace` and `\overbrace` commands, which you could use as
``````\$\underbrace{P(X \mid O)}_{p_1} \propto \overbrace{P(X)P(O \mid X)}^{p_2}\$.