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## Numbered Equations

Recall that in-line math is produced by using single dollar signs, $...$, and displayed equations are produced by using double dollar signs, $$...$$. To produce a numbered equation, use the equation environment; for example,

$$\chi(M_g) = 2-2g,$$
produces

Note that the equation environment puts you in math mode, so there is no need to use $$...$$ around the $$...$$.

If you want to refer to a numbered equation, you can put a \label{ } command between the and the . Then the key will be associated with the number of the equation, and you can reference the equation by typing, for example,

...as we see from (\ref{eqnkey}).
See Section 6.8 above for explanations of the \label{ } and \ref{ } commands.

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