Atn(number)
Returns the arctangent of a number. The arctangent is the angle whose tangent is number.
See also Tan, Sin, Cos, and Pi.
Tangent of the angle you want.
The range of the result is -Pi/2 to Pi/2 radians. To convert degrees to radians, multiply degrees by Pi/180. To convert radians to degrees, multiply radians by 180/Pi.