atan(value)
The inverse of tan(), returns the arc tangent of a value. This function expects the values in the range of -1 to 1 and values are returned in the range 0 to PI (3.1415927).
Type: function
Parameter(s):
- value {Number}:The value whose arc tangent is to be returned. 
Returns:
- 
    {Number}:
 The arc tangent.