ATAN returns the inverse trigonometric tangent of a number.

## Syntax

ATAN (`number`)

This
function returns the inverse trigonometric tangent of `number`,
which is the angle (in radians) whose tangent is Number. The angle
returned is between -PI/2 and PI/2.

## Example

`=ATAN(1)` returns ` 0.785398163397448
(PI/4 radians).`.

`=DEGREES(ATAN(1))` returns `45`.
The tangent of 45 degrees is 1.