November 2002
Intermediate to advanced
640 pages
16h 33m
English
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2.12. Doing Trigonometry in Degrees, not Radians
Problem
You have numbers in degrees but want to use the trigonometric functions.
Solution
Use deg2rad( )
and rad2deg( ) on your
input and output:
$cosine = rad2deg(cos(deg2rad($degree)));
Discussion
By definition, 360 degrees is equal to 2π radians, so
it’s easy to manually convert between the two
formats. However, these functions use PHP’s internal
value of π, 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.
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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