# different values of integral with/without bogus assumptions

I do not understand why I get different answers for the following two identical integrals.

Integrate[Cos[10*Pi (z - x)], {x, 1/10, 1}, Assumptions :> {}]
Integrate[Cos[10*Pi (z - x)], {x, 1/10, 1}, Assumptions :> {x > 0}]


Output (respectively):

-Sin[10Pi*z]/5Pi
Sin[10Pi*z]/5Pi


Running version 9. Any help would be very appreciated. Thanks!

-
I get the same output for each line from version 10.0.0 under Windows. What version are you running and what output do you get? –  Mr.Wizard Aug 27 at 22:06
What did you get? I've checked results im Mathematica versions 7 and 10; they were the same however in version 8 the results were different by the sign (a bug). –  Artes Aug 27 at 22:06
Updated question- have similar sign issue in 9.0.0. So (-) is correct? –  StarStrides Aug 27 at 22:16
There were certain problems in ver. 8 with Integrate, they have been fixed though not all, see e.g. Mathematica gives wrong answer for an integral, in ver. 9: Mathematica 9 can't integrate this function but earlier versions could or Bug in analytic integration? –  Artes Aug 27 at 22:19
This is a trivial excersise, so you shouldn't ask, just verify it! –  Artes Aug 27 at 22:22