Command: arctan
  
Syntax: 
  x2 = arctan(x1)
  
Description: 
  Return the arctangent of x1.
  
Comments: 
  The result will always be in the range -pi/2 to +pi/2 radians.
  
  This function may be applied to an atom or to all elements
  of a sequence.
  
Example: 
     s = arctan({1,2,3})
              -- s is {0.785398, 1.10715, 1.24905}

See Also: 
  tan, sin, cos
  
