& atan()
 
  Syntax: atan(<number>)
 
  Returns the arctangent of <number>, expressed in radians.
 
  Example:
 
  > say atan(0)
  You say "0"
  > say atan(1)
  You say "0.785398"
  > say atan(1.557408)
  You say "1"
 	
  See Also: acos(), asin(), cos(), pi(), sin(), tan().