{{fbdoc item="title" value="ATN"}}----
Returns the arctangent of a number

{{fbdoc item="syntax"}}##
	[[KeyPgDeclare declare]] [[KeyPgFunction function]] **Atn** ( [[KeyPgByval byval]] //number// [[KeyPgAs as]] [[KeyPgDouble double]] ) [[KeyPgAs as]] [[KeyPgDouble double]]
##
{{fbdoc item="usage"}}##
	//result// = Atn( //number// )
##
{{fbdoc item="param"}}
	##//number//##
		A number.

{{fbdoc item="ret"}}
	The angle, in radians, whose tangent is ##//number//##, in the range [-Pi/2..Pi/2].

{{fbdoc item="desc"}}
	##Atn## returns the arctangent of the argument ##//number//## as a ##[[KeyPgDouble Double]]## within the range of -[[TutMathAngles Pi]]/2 to [[TutMathAngles Pi]]/2.  The arctangent is the inverse of the ##[[KeyPgTan Tan]]## function. The returned angle is measured in [[TutMathAngles radians]] (not [[TutMathAngles degrees]]).

{{fbdoc item="ex"}}
{{fbdoc item="filename" value="examples/manual/math/atn.bas"}}%%(freebasic)
PRINT "Pi ="; ATN ( 1.0 ) * 4
PRINT ATN ( 4 / 5 )
%%

The output would be:
%%
Pi = 3.141592653589793
0.6747409422235527
%%

{{fbdoc item="diff"}}
	- None

{{fbdoc item="see"}}
	- ##[[KeyPgTan Tan]]##
	- ##[[KeyPgAtan2 ATan2]]##
	- [[TutMathIntroTrig A Brief Introduction To Trigonometry]]

{{fbdoc item="back" value="CatPgMath|Math"}}