@Kitonum You are right, i figured that out myself, but thanks anyway :) Its a bit shorter that what i did, so thanks again.

@Markiyan Hirnyk It works thanks.

@Carl Love Thanks the Int instead of int worked. Now it only takes seconds to calc!!

Sorry. Here it is plain text:

int(sqrt(1+(diff(f(x), x))^2), x = 0 .. 17)

And the function i have defined, but forgot to tell you about:

f := proc (x) options operator, arrow; (-1)*0.167e-1*x^3+.3165*x^2 end proc

And the result:

30.75115129-1.376953493*10^(-8)*I

I just need the:

30.75115129 part, not the part with I. It takes very long for maple to calc that :)

Thanks again in advance!

Thanks! It works! :)