ATAN
Returns an angle, in radians, with a tangent of the specified angle. The result is
between -pi/2 and +pi/2.
Syntax
ATAN(Value)
Value is a number or a formula that
returns a number.
Example
This example returns 0.7854 (pi/4 or 45 degrees):
ATAN(1)
This example returns 0:
ATAN(0)