182 ATN arc-tangent Purpose To calculate an angle whose tangent is known. The calculated angle is in radians but may be converted to degrees by using the function DEG . Examples 240 value=DEG(ATN(22.31)) 1250 X=ATN(Y) A function giving the arc-tangent of its argument. The result is in radian measure. Description Syntax = ATN ( ) Associated keywords ACS , ASN , SIN , COS , TAN , RAD , DEG