# Expressions

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## General

Expressions are a feature of the SimGear library and provide a nice way of implementing complex math formulas using XML syntax. They are supported in many systems within the FlightGear code.

## Usage

Expressions are supported in

## Sample Expressions

This is a sample expression for c = sqrt(a*a + b^2)

<expression>
<sqrt>
<sum>
<product>
<property>/value/a</property>
<property>/value/a</property>
</product>
<pow>
<property>/value/b</property>
<value>2</value>
</pow>
</sum>
</sqrt>
</expression>

## Supported elements

<acos>
<asin>
<atan>
<ceil>
<cos>
<cosh>
<exp>
<floor>
<log>
<log10>
<sin>
<sinh>
<sqrt>
<tan>
<tanh>
<atan2>
<div>
<mod>
<pow>
<value>
<property>
<abs> (same as fabs)
<sqr>
<clip>
<div>
<mod>
<sum>
<difference> (same as dif)
<product> (same as prod)
<min>
<max>
<table>