0.9.5/api/a00031_source.html

 #ifndef GLM_GTX_fast_trigonometry

 #define GLM_GTX_fast_trigonometry


 // Dependency:

 #include "../glm.hpp"


 #if(defined(GLM_MESSAGES) && !defined(GLM_EXT_INCLUDED))

 #       pragma message("GLM: GLM_GTX_fast_trigonometry extension included")

 #endif


 namespace glm

 {


     template <typename T>

         T fastSin(const T& angle);


         template <typename T>

         T fastCos(const T& angle);


         template <typename T>

         T fastTan(const T& angle);


         template <typename T>

         T fastAsin(const T& angle);


     template <typename T>

         T fastAcos(const T& angle);


         template <typename T>

         T fastAtan(const T& y, const T& x);


     template <typename T>

         T fastAtan(const T& angle);


 }//namespace glm


 #include "fast_trigonometry.inl"


 #endif//GLM_GTX_fast_trigonometry

glm::fastAcos
T fastAcos(const T &angle)
Faster than the common acos function but less accurate.

glm::fastAtan
T fastAtan(const T &y, const T &x)
Faster than the common atan function but less accurate.

glm::angle
GLM_FUNC_DECL T angle(detail::tquat< T, P > const &x)
Returns the quaternion rotation angle.

glm::fastAsin
T fastAsin(const T &angle)
Faster than the common asin function but less accurate.

glm::fastTan
T fastTan(const T &angle)
Faster than the common tan function but less accurate.

glm::fastSin
T fastSin(const T &angle)
Faster than the common sin function but less accurate.

glm::fastCos
T fastCos(const T &angle)
Faster than the common cos function but less accurate.