Software to calculate integrals

[Yeti]

I know this isn't the most ideal forum, but is there any free good software? Or is there really only commercial stuff like Maple/MATLAB to choose from.

If the latter is true, if someone who has either of these could quickly run the integral of sin^6(t) between 0 and pi/2, then I could check my answer, that would also be cool.

Thanks.