2.13. Doing Trigonometry in Degrees, not Radians2.13.2. SolutionUse deg2rad( ) and rad2deg( ) on your input and output: $cosine = rad2deg(cos(deg2rad($degree))); 2.13.3. DiscussionBy 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 highprecision answer. To access this number for other calculations, use the constant M_PI, which is 3.14159265358979323846. There is no builtin support for gradians. This is considered a feature, not a bug. 2.13.4. See AlsoRecipe 2.13 for trig basics; documentation on deg2rad( ) at http://www.php.net/deg2rad and rad2deg( ) at http://www.php.net/rad2deg. Copyright © 2003 O'Reilly & Associates. All rights reserved. 
