====== ATN ======

(Defined in //[[trigono.bas]]//)

The ''ATN()'' function returns the arctangent of the argument. It is the inverse function of [[TAN]].

===== Function header =====

<code xcbasic>
DECLARE FUNCTION ATN AS FLOAT (x AS FLOAT) SHARED STATIC
</code>

<adm warning>
You must include the //TRIGONO.BAS// library in your program before you call this function.
</adm>

===== Example =====

<code xcbasic>
INCLUDE "trigono.bas"
PRINT ATN(0.5) ' will output 0.464088
</code>

<adm note>
Trigonometric functions in XC=BASIC were designed to be fast rather than accurate. The result is accurate to 3 to 4 decimal digits (the error range is 0 to 0.0006). Please see [[http://www.ganssle.com/approx.htm|this article]] for details.
</adm>
===== See also =====

  * [[TAN]]
  * [[SIN]]
  * [[COS]]