Module root_find 

Scalar root-finding helpers used by implied vol and other solvers.

Method	Use in this crate
Newton–Raphson	Primary IV step when vega is reliable
Brent	Robust bracketed fallback after Newton

Brent combines bisection reliability with secant / inverse-quadratic speed on smooth problems. We previously used plain bisection as the fallback; Brent is the standard upgrade for the same bracketed contract.

Functions

brent_root

Find a root of continuous f on bracket [lo, hi] (Brent 1973).