Function agm_elliptic_perimeter

fn agm_elliptic_perimeter(accuracy: f64, radii: Vec2) -> f64

Calculates circumference C of an ellipse with radii (x, y) using the arithmetic-geometric mean, as described in equation 19.8.6 of https://web.archive.org/web/20240926233336/https://dlmf.nist.gov/19.8#i.