### 4.4.3 `fsolve` or `nSolve` with the option `falsepos_solver`

The "false position" algorithm is an iterative algorithm based on linear
interpolation : we compute the value of *f* at the intersection of the line
(*a*,*f*(*a*)), (*b*,*f*(*b*)) with the *x* axis. This value gives us the part of the
interval containing the root, and on which a new iteration is performed.

The convergence is linear but generically faster than bisection.

Input :

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

Output :

`[0.739085133215,0.739085133215]`