###Function###
ATan

###Description###
Calculates the arctangent of a number.

###Syntax###
ATan ( expression )


###Parameters###
@@ParamTable@@
expression
	Any valid numeric expression.
@@End@@

###ReturnValue###
Returns the trigonometric arctangent of <i>expression</i>.  Result is in radians.



###Remarks###
The result of <b>4 * ATan(1)</b> is pi.

###Related###
Sin, Cos, Tan, ASin, ACos


###Example###
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