ATN

The ATN function returns the arctangent of a number.

ATN( number )

The number argument can be any valid numeric expression.

The ATN function takes the ratio (number) of two sides of a right triangle and returns the corresponding angle. The ratio is the length of the side opposite the angle divided by the length of the side adjacent to the angle. The result is expressed in radians and is in the range -Pi/2 to Pi/2 radians. Pi is approximately 3.141593.

To convert degrees to radians, multiply degrees by Pi/180. To convert radians to degrees, multiply radians by 180/Pi.

Because of sign ambiguity, ATN() cannot determine with certainty the quadrant in which the angle falls. ATN2() can be used if you need to determine the quadrant.