# ATN2¶

Returns the inverse tangent of the ratio of x and y.

ATN2(y,x) = ATAN(y/x)

This represents the angle in radians from the positive x-axis of a plane and the point (x, y) on it, with positive sign for the upper half-plane.

## Syntax¶

ATN2( expr1, expr2 )


## Arguments¶

Parameter Description
expr1 Numeric expression representing the y component.
expr2 Numeric expression representing the x component

## Returns¶

Always returns a floating point result of the inverse tangent, in radians.

## Notes¶

• The result is given in radians, in the range (-π, π].
• If the input value is NULL, the result is NULL.

## Examples¶

### Inverse tangent of (1, 0) (= π/2)¶

numbers=> SELECT ATN2(1,0);
atn2
----
1.5707963267948966


### Inverse tangent of x=0.5, y=SQRT(3)/2 (= π/3, or 60°)¶

Use SQRT to simplify input and DEGREES to convert the result from radians.

numbers=> SELECT ATN2(0.5*SQRT(3), 0.5), DEGREES(ATN2(0.5*SQRT(3), 0.5));
atn2   | degrees
-------+--------
1.0472 |      60