# Help:Equations

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## General rules

**<math>...</math>**- formula must be in MATH tag.**\frac{first line}{second line}**- fraction

**\cdot**- multiplication sign (don't use x, unless you multiply arrays)

**\sqrt{}**- square root

**σ**- greek letters

**Failed to parse (syntax error): {\displaystyle σ}**

**\sum_{k=1}^N k^2**- sum, power

Full rules are available on Mediawiki site: Formula.

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