### 4.4.2 `fsolve` or `nSolve` with the option `brent_solver`

The Brent method interpolates of *f* at three points, finds
the intersection of the interpolation with the *x* axis, computes
the sign of *f* at this point and chooses the interval where the sign changes.
It is generically faster than bisection.

Input :

`fsolve((cos(x))=x,x,-1..1,brent_solver)`

Output :

`[0.73908513321 5,0.739085133215]`