Function auxlat_convert_full 

pub fn auxlat_convert_full(
    szeta: f64,
    czeta: f64,
    seta: &mut f64,
    ceta: &mut f64,
    f: &[f64],
    k: i32,
)

Convert auxiliary latitude zeta to eta, given coefficients F produced by pj_auxlats_coeffs(n, zeta, eta, F). K is the size of F (defaults to AuxLat::ORDER). In this signature, the sine and cosine of eta are returned. This provides high relative accuracy near the poles.