A function giving the arc tangent of its argument in radians. The permitted range of the argument is from - to + infinity.

By convention, the result will be in the range -`PI`/2 to +`PI`/2 (-90 to +90 degrees).

If you know the tangent of the angle, this function will tell you the angle (in radians).

As the magnitude of the argument (tangent) becomes very large (approaches + or - infinity) the accuracy diminishes.

In the example below, *radian_angle* becomes equal to the angle (in radians) whose tangent is *y*.

radian_angle=ATN(y)

You can convert the answer to degrees by using the `DEG` function. (The `DEG` function is equivalent to multiplying by 180/`PI`.) The example below is similar to the first one, but the angle is in degrees.

degree_angle=DEG(ATN(y))

## Syntax

`<n-var>=ATN(<numeric>)`