Previous Next JavaScript must be enabled to correctly display this content

## arc tan function

The `atan` function is an inverse trigonometric function. The `atan` function returns the arc tangent (inverse of tangent) of the input expression.

Syntax:

    double atan(n)

Semantics:

- n: The argument n is an expression that resolves to a number.
- return type: double.

  The resultant angle is expressed in radians and is in the range -pi/2 through -pi/2 with the following exceptions:

  - Returns a NULL value in the following cases:
    - n resolves to a NULL value
    - n does not resolve to a number
  - Returns NaN if n resolves to NaN.
  - Results in a zero with the same sign as n, when n is zero.

Example 12-74 arc tan function

    SELECT atan(n) FROM Archery

Value of n | Output
--- | ---
1 | 0.7853981633974483
sqrt(3) | 1.0471975511965976