Returns the inverse tangent of a value.
Synopsis
result = ATan(value1, value2)
Args
value is a number in the range of -1 to 1, if value2 is omitted.
Returns
If value2 is omitted, then ATan returns the inverse tangent of value1 in the range -(PI/2) to PI/2).If value2 is specified, then it returns the inverse tangent of value1 / value2 in the range indicated by the signs of the arguments. For example, if value1 is positive and value2 is negative, then the result is in the range PI/2 to PI.