Function semi_major_axis_from_apsides 

pub fn semi_major_axis_from_apsides(
    periapsis_radius: f64,
    apoapsis_radius: f64,
) -> Option<f64>

Computes the semi-major axis from periapsis and apoapsis radii.

Formula: a = (r_p + r_a) / 2

Returns None when either radius is less than or equal to zero, when apoapsis_radius is less than periapsis_radius, or when the input or result is not finite.

Examples

use use_orbit::semi_major_axis_from_apsides;

assert_eq!(semi_major_axis_from_apsides(10.0, 20.0), Some(15.0));