The ATAN function returns the arc tangent of a specified number.

The specified number is the tangent, in radians, of the angle
that you want. The specified number must be a DOUBLE
PRECISION number.

- If the specified number is NULL, the result of this function is NULL.
- If the specified number is zero (0), the result of this function is zero with the same sign as the specified number.

The returned value, in radians, is in the range -pi/2 to pi/2. The data type of the returned value is a DOUBLE PRECISION number.

ATAN (number)