Very useful answers. Thank you.

@acer Many thanks. Just the kind of thing I was looking for. I also found a solution using disassembly posted below.

Cheers.

@Markiyan Hirnyk That would be most helpful. 

Many Thanks. 

@Markiyan Hirnyk Many thanks for the reply. Unfortunately it doesn't seem to work for me. I am using Maple 2015. 

I just get the same expression back again (in the same form). Do i need to add any packages using with()

Thanks.

Double checked this on my 2015. Seems to work fine for me as well.

restart; with(LinearAlgebra); Digits := 50; n := 5; M := [seq(cos(Pi*j/n), j = 0 .. n)]; V := VandermondeMatrix(M);
c1 := ConditionNumber(V); c1 := simplify(%); evalf(c1);
119.99999998441425700422839483204069898827891371052

For n:=3 and 4 I get 16. and 40. respectively. 

Hope that helps.

Cheers.

By the way this is definitely there in 2015 as well although intermittently. If you notice that Maple has rearranged your original input it is bad news. Once again running the entire script 3 times (using !!!) always fixes it.

Breaking up the expressions to less than 24 inputs and then combining them seems to always work. 

expr1a := a+b+c+d+e+f+g+h+i+j+k;
a + b + c + d + e + f + g + h + i + j + k
expr1b := l+m+n+o+p+q+r+s+t+v-w+w+x+y;
l + m + n + o + p + q + r + s + t + v + x + y

expr2a := a+b+c+d+e+f+g+h+i+j+k;
a + b + c + d + e + f + g + h + i + j + k
expr2b := l+m+n+o+p+q+r+s+t+v-w+w+x+y;
l + m + n + o + p + q + r + s + t + v + x + y

expr1 := expr1a+expr1b;
a + b + c + d + e + f + g + h + i + j + k + l + m + n + o + p + q + r + s + t + v + x + y

expr2 := expr1a+expr2b;
a + b + c + d + e + f + g + h + i + j + k + l + m + n + o + p + q + r + s + t + v + x + y

expr1-expr2;
0

Noticed that if you rerun the entire worksheet (using !!!) a few times it always works the third time. (Maybe thats why there are three exclamation points).

@rlopez thanks, that would explain why.