Doing Trigonometry in Degrees, not Radians (PHP Cookbook)

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2.13. Doing Trigonometry in Degrees, not Radians

2.13.1. Problem

You have numbers in degrees but want to use the trigonometric functions.

2.13.2. Solution

Use deg2rad( ) and rad2deg( ) on your input and output:

$cosine = rad2deg(cos(deg2rad($degree)));

2.13.3. Discussion

By definition, 360 degrees is equal to 2 radians, so it's easy to manually convert between the two formats. However, these functions use PHP's internal value of , so you're assured a high-precision answer. To access this number for other calculations, use the constant M_PI, which is 3.14159265358979323846.

There is no built-in support for gradians. This is considered a feature, not a bug.

2.13.4. See Also

Recipe 2.13 for trig basics; documentation on deg2rad( ) at http://www.php.net/deg2rad and rad2deg( ) at http://www.php.net/rad2deg.

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