Function mean_one_minus_cos 

pub fn mean_one_minus_cos(probability: &[f64], quantiles: &[f64]) -> f64

⟨1 - cos θ⟩ of a stored inverse-CDF row, integrated exactly over the piecewise-linear θ(u) that CrossSectionTable::inverse_cdf interpolates. σ_tr1 = σ_el ⟨1 - cos θ⟩.