### Circular Trigonometric Functions

Function: double gsl_sf_sin (double x)
Function: int gsl_sf_sin_e (double x, gsl_sf_result * result)
  These routines compute the sine function \sin(x).

Function: double gsl_sf_cos (double x)
Function: int gsl_sf_cos_e (double x, gsl_sf_result * result)
  These routines compute the cosine function \cos(x).

Function: double gsl_sf_hypot (double x, double y)
Function: int gsl_sf_hypot_e (double x, double y, gsl_sf_result * result)
  These routines compute the hypotenuse function \sqrt{x^2 + y^2} avoiding overflow and underflow.

Function: double gsl_sf_sinc (double x)
Function: int gsl_sf_sinc_e (double x, gsl_sf_result * result)
  These routines compute \sinc(x) = \sin(\pi x) / (\pi x) for any value of x.