find....

- anonymous

find....

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- anonymous

|dw:1437386418657:dw|

- Astrophysics

let u = cosx

- anonymous

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

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## More answers

- Astrophysics

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

- dan815

|dw:1437386882138:dw|

- anonymous

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

- anonymous

|dw:1437386925478:dw|

- dan815

|dw:1437386942356:dw|

- Astrophysics

|dw:1437386975349:dw|

- anonymous

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

- Astrophysics

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

- Astrophysics

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

- Astrophysics

|dw:1437387169151:dw|

- UsukiDoll

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

- Astrophysics

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

- UsukiDoll

|dw:1437387304792:dw|

- Astrophysics

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

- UsukiDoll

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

- 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

- Astrophysics

What ever works for you :P

- anonymous

ohh.. i thought it was done. how?

- UsukiDoll

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

- Astrophysics

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

- UsukiDoll

|dw:1437387439915:dw|

- Astrophysics

Or pi/3* not negative :P

- anonymous

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

- Astrophysics

or is that suppose to be -pi/3?

- UsukiDoll

|dw:1437387518604:dw|

- Astrophysics

or pi/3 idk

- Astrophysics

Yes you should get 15/64

- Astrophysics

So it is pi/3

- UsukiDoll

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

- Astrophysics

Lol I have no clue what the intervals are

- 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

- Astrophysics

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

- anonymous

srry -pi/3

- Astrophysics

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

- UsukiDoll

|dw:1437387699526:dw|

- UsukiDoll

got em....

- UsukiDoll

15/64 = 0.234375

- UsukiDoll

I just evaluated...

- Astrophysics

|dw:1437387751936:dw| right?

- UsukiDoll

yeah

- Astrophysics

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

- Astrophysics

|dw:1437388080251:dw| right?

- UsukiDoll

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

- Astrophysics

It doesn't matter, cosx is an even function

- anonymous

yeah. thats where it started falling off.

- Astrophysics

|dw:1437388278120:dw|

- ali2x2

a clif?

- ali2x2

:P

- 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

- ali2x2

:o

- ali2x2

lol i saw that

- Astrophysics

Does that make sense though @Xlegalize

- anonymous

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

- ali2x2

Nice work everyone now i rest me case

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