- f is the function to be approximated.
- I is the interval where the function must be approximated.
- eps is the maximal acceptable error.
- w (optional) is a weight function. Default is 1.

- guessdegree tries to find the minimal degree needed to approximate f on I by a polynomial with an error err=p*w-f whose infinity norm not greater than eps. More precisely, it finds n minimal such that there exists a polynomial p of degree n such that ||p*w-f|| < eps.
- guessdegree returns an interval: for common cases, this interval is reduced to a
single number (e.g. the minimal degree). But in certain cases, guessdegree does
not succeed in finding the minimal degree. In such cases the returned interval
is of the form [n,p] such that:
- no polynomial of degree n-1 gives an error less than eps.
- there exists a polynomial of degree p giving an error less than eps.

[10;10]

[8;9]