fn tau_factor<const N: usize>(
l: i32,
m: i32,
[upper, lower]: [Jet<N>; 2],
cosine: Jet<N>,
) -> Jet<N>Expand description
tau_l^m / sin(theta)^(|m|-1) for m != 0 from one Legendre recurrence, by DLMF
14.10.5: sin(theta) tau = l cos(theta) P_l^m - (l + m) P_(l-1)^m.