C Math atan2() Function

Example

Return the angle in radians of the polar coordinates given rectangular coordinates:

``````printf("%f", atan2(0.5, 0.5));
printf("%f", atan2(-0.5, -0.5));
printf("%f", atan2(5, 5));
printf("%f", atan2(10, 20));
printf("%f", atan2(5, -5));
printf("%f", atan2(-10, 10));
``````
Try it Yourself »

Definition and Usage

The `atan2()` function returns the angle theta in radians from the conversion of rectangular coordinates (x, y) to polar coordinates (r, theta).

This is similar to calling atan(y/x) but it takes into account negative values of x so that it can return angles outside of the range -PI/2 to PI/2.

The `atan2()` function is defined in the `<math.h>` header file.

Note: In the `atan2()` method the y coordinate goes first, then the x coordinate. This is because it is equivalent to the arctangent of the division y / x.

Syntax

One of the following:

``atan2(double y, double x);``

Parameter Values

Parameter Description
y Required. The y coordinate of the point to find the angle of.
x Required. The x coordinate of the point to find the angle of.

Technical Details

Returns: A `double` value representing the angle in radians that a point (x, y) makes around the origin (0, 0).

Related Pages

C Functions Tutorial

C Math Functions Tutorial

×

Contact Sales

If you want to use W3Schools services as an educational institution, team or enterprise, send us an e-mail:
sales@w3schools.com