### 30.3 Auxiliary Functions

The following functions provide information about an existing Chebyshev series.

Function: size_t gsl_cheb_order (const gsl_cheb_series * cs)

  This function returns the order of Chebyshev series cs.

Function: size_t gsl_cheb_size (const gsl_cheb_series * cs)
Function: double * gsl_cheb_coeffs (const gsl_cheb_series * cs)

  These functions return the size of the Chebyshev coefficient array `c[]` and a pointer to its location in memory for the Chebyshev series cs.