## anonymous 5 years ago how do you integrate (x^9)(cos(x^5))?

1. anonymous

$intx ^{9}cosx ^{5}dx.$

2. anonymous

Possibly integration by parts

3. anonymous

i realize that, but should i don't know what values to assign for u and dv. should i substitute before i even use integration by parts?

4. anonymous

Try x^9 as u

5. anonymous

((x^10)/10)(-sinx(x^5))

6. anonymous

What is that Nick, like the teacher says, show your work.

7. anonymous

okay Integrate (x^9)we get (x^9+1)/(9+1) intregrate cos(x^5) we get -sin(x^5)

8. anonymous

But there is a rule, the two x quantities are multiplied, so you can't integrate straight out, right?

9. anonymous

yeah, so you integrate by parts.

10. anonymous

yes

11. anonymous

substituting u for x^9 doesn't seem to work chaguanas ...

12. anonymous

Check this I haven't done integration by parts in a while$x ^{9}\cos x ^{5}-45x ^{5}\sin x ^{5}$

13. anonymous

+C

14. watchmath
15. watchmath

wolframalpha will give you the steps as well.

16. anonymous

hold on are you sure that the integral of cos x^5 is is -sin x^5 - try differentiating -sin x^5.

17. anonymous

Yeah, mine is wrong, see the wolfram watchmath put up. That was the u sub that ecollison was talking about, I missed that.

18. anonymous

watchmath thanks! the link was right

19. anonymous

But please explain the u sub, they didn't account for the x^9 fully.

20. anonymous

u=x^5 not x^9

21. anonymous

lols