how to understand the dist?

[tangjuju]

No description provided.

[tangjuju]

dist = b * (ca.sqrt((c ** 2 / a ** 2 + s ** 2 / b ** 2) * center_vec[0] ** 2 + (s ** 2 / a ** 2 + c ** 2 / b ** 2) *
center_vec[1] ** 2 + 2 * c * s * (1 / a ** 2 - 1 / b ** 2) * center_vec[0] * center_vec[1]) - 1) - safe_dist

[Amourvc]

I'm having the same problem, comparing with formula 7 of the paper, can't understand this formula