can the prime really not solve this integral?

[CR Haeger]

(02-27-2014 12:21 PM)parisse Wrote:  You get a numeric answer with:
int(x^3/(exp(x)-1),x,0,inf)
then shift-enter.
x^3/(exp(x)-1) does not have an antiderivative than you can express with elementary function (special functions required, polylogs here). There is probably a trick than can give you the exact answer (pi^4/15) for the definite integral, any idea? On a voyage 200, you don't get the exact value by the way.

Thanks - I keep forgetting to use shift enter.

Hitting "a b/c" seems to convert 6.49 to the fraction equivalent to pi^4/15.