Function robust_geo::sign_det_x2y2_plus_2x_det_x

pub fn sign_det_x2y2_plus_2x_det_x(
    a: Vector2<f64>, 
    b: Vector2<f64>, 
    u: f64, 
    i: f64, 
    j: f64
) -> f64

Computes the following sum of determinants.

│ a.x^2 + a.y^2   1 │ + 2u│ i   1 │
│ b.x^2 + b.y^2   1 │     │ j   1 │

and returns a number with the same sign as the sum, or 0 if the sum is 0