## anonymous one year ago find....

1. anonymous

|dw:1437386418657:dw|

2. Astrophysics

let u = cosx

3. anonymous

ahh. I chose sin x. alright ´give me a moment to solve this.

4. Astrophysics

Naw, you will see why to, and np take your time

5. dan815

|dw:1437386882138:dw|

6. anonymous

okey so $\frac{ du }{ dx }=-\sin x$ $\sin dx =-du$ $\int\limits_{0}^{py/3} u^{3} *-1 du$ then you get

7. anonymous

|dw:1437386925478:dw|

8. dan815

|dw:1437386942356:dw|

9. Astrophysics

|dw:1437386975349:dw|

10. anonymous

so my final answer was |dw:1437387078578:dw|

11. Astrophysics

|dw:1437387056540:dw| dont forget to change the limits

12. Astrophysics

When you're making a u sub make sure to change the limits as well

13. Astrophysics

|dw:1437387169151:dw|

14. UsukiDoll

I would just sub that u back after we take the antiderivative so I won't have to change limits :P

15. Astrophysics

Or yeah you can do it that way, it doesn't really matter

16. UsukiDoll

|dw:1437387304792:dw|

17. Astrophysics

I just like doing it this way, it sometimes saves time haha

18. UsukiDoll

it's only half done @Xlegalize next you have to evaluate the integral

19. UsukiDoll

wahhhhhhhh I don't wanna sub old limits and get new ones ......... I rather just sub u back after antiderivative step and just evaluate so easier lezl

20. Astrophysics

What ever works for you :P

21. anonymous

ohh.. i thought it was done. how?

22. UsukiDoll

it was half done.. evaluating was missing at x = 0 cos(0) is 1

23. Astrophysics

Oh, you have to use fundamental theorem of calculus still so |dw:1437387420691:dw|

24. UsukiDoll

|dw:1437387439915:dw|

25. Astrophysics

Or pi/3* not negative :P

26. anonymous

thats exactly what I did after I got the answer 0.265, the correct is 0.234

27. Astrophysics

or is that suppose to be -pi/3?

28. UsukiDoll

|dw:1437387518604:dw|

29. Astrophysics

or pi/3 idk

30. Astrophysics

Yes you should get 15/64

31. Astrophysics

So it is pi/3

32. UsukiDoll

pi/3 is 1.04 something.. that's not 0.2.34

33. Astrophysics

Lol I have no clue what the intervals are

34. anonymous

soo strange.. now I get the right answer. maybe it depends on how I plug it into the calc? tho it shouldnt. But I did like this. -cos(pi/3)^4/4+cos(0)^4/4

35. Astrophysics

is that suppose to be pi/3 or -pi/3

36. anonymous

srry -pi/3

37. Astrophysics

Oh ok, let me just show you how to do it your way then

38. UsukiDoll

|dw:1437387699526:dw|

39. UsukiDoll

got em....

40. UsukiDoll

15/64 = 0.234375

41. UsukiDoll

I just evaluated...

42. Astrophysics

|dw:1437387751936:dw| right?

43. UsukiDoll

yeah

44. Astrophysics

|dw:1437387930922:dw| I'm doing it exactly the way you were doing/ would do it, just to make it clear.

45. Astrophysics

|dw:1437388080251:dw| right?

46. UsukiDoll

hey waitttt.... we have -pi/3 meaning -1/2

47. Astrophysics

It doesn't matter, cosx is an even function

48. anonymous

yeah. thats where it started falling off.

49. Astrophysics

|dw:1437388278120:dw|

50. ali2x2

a clif?

51. ali2x2

:P

52. Astrophysics

It doesn't really matter in this question though as it's ^4 meaning it will be positive anyways but yes, cosx is an even function :O

53. ali2x2

:o

54. ali2x2

lol i saw that

55. Astrophysics

Does that make sense though @Xlegalize

56. anonymous

Alright, it has been done:D Thanks for all ur time and help and patience.

57. ali2x2

Nice work everyone now i rest me case