Futurebasic/Language/Reference/atn

Function
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Syntax
radianAngle# = atn( expr )

Description
Returns the arctangent of  in radians. In other words, if  represents the tangent of some angle, then      returns the angle. The returned angle will be in the range of -π/2 to +π/2 radians (which corresponds to -90 to +90 degrees). always returns a double-precision result.

Example
Because   equals π/4, you can use   to get a value for π. dim pi# end globals

pi = atn( 1 ) * 4 print pi Program output: 3.14159265359