### 8.4.2 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]