Recipe 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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