In SQL Server, the ATN2() function returns the arctangent between two values. Specifically, it returns the angle, in radians, between the positive x-axis and the ray from the origin to the point (y, x), where x and y are the values of the two specified float expressions.

You provide the values as arguments when calling the function.

Syntax

The syntax goes like this:

ATN2 ( float_expression , float_expression )

Where float_expression is an expression of data type float.

Example 1 – Basic Usage

Here’s a basic example that returns the arc tangent of two values.

SELECT ATN2(2, 3) Result;

Result:

+-------------------+
| Result            |
|-------------------|
| 0.588002603547568 |
+-------------------+

And with another set of values.

SELECT ATN2(1.3, 235.70) Result;

Result:

+---------------------+
| Result              |
|---------------------|
| 0.00551542985993961 |
+---------------------+

Example 2 – Negative Values

And with negative values.

SELECT ATN2(-1.3, -235.70) Result;

Result:

+-------------------+
| Result            |
|-------------------|
| -3.13607722372985 |
+-------------------+

And with a positive and a negative:

SELECT ATN2(1.3, -235.70) Result;

Result:

+------------------+
| Result           |
|------------------|
| 3.13607722372985 |
+------------------+

Example 3 – Expressions

You can also pass in expressions like this:

SELECT ATN2(2.5 + 0.3, 5) Result;

Result:

+-------------------+
| Result            |
|-------------------|
| 0.510488321916776 |
+-------------------+

Example 4 – Passing in a Function

In this example I pass in the T-SQL PI() function as one of the arguments.

SELECT ATN2(PI(), 2) Result;

Result:

+------------------+
| Result           |
|------------------|
| 1.00388482185389 |
+------------------+