(atan)

(atof)

(atan number1 [number2])

Calculate the arctangent.

This function returns the principle arc tangent of the quotient number1 divided by number2. If number2 is not supplied, it is assumed to be 1.0, thus returning the principle arctan of number1. The value returned is always between -pi/2 and pi/2 radians.

Examples

Code	Returns
(atan 0.25)	0.24498
(atan -2)	-1.10715
(atan 1.0 0.75)	0.927295

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Programming Overview of LISP (LISt Processing) Language