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** monter:** Solve equations with fsolve
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The secant methode is a simplified version of the Newton method.
The computation of *x*_{1} is done using the Newton method.
The computation of
*f'*(*x*_{n}), *n* > 1 is done approximatively.
This method is used when the
computation of the derivative is expensive:

*x*_{i+1} =

*x*_{i} -

,

*f'*_{est} =

The convergence for roots of multiplicity 1
is of order
(1 + )/2 1.62....

Input :
`fsolve((cos(x))=x,x,-1..1,secant_solver)`

Output :
`[0.739085078239,0.739085137844]`

Input :
`fsolve((cos(x))=x,x,0,secant_solver)`

Output :
`0.739085133215`

giac documentation written by Renée De Graeve and Bernard Parisse