intergration by parts? (1 Viewer)

[fullonoob]

i wna see if my answer is right

i did integration by parts twice, but my answer seems wrong still cos i've never seen sin2, cos2 o-o
i got 8sin2 -4cos2 - 4

 

[omgmynameislong]

Got

-x^2cosx+2xsinx -2cosx

cbf subbing limits in.

 

[fullonoob]

i changed it to 2 integral whatever limit 0 2 and cbf subbing in your limits as well :x

 

[Drongoski]

i wna see if my answer is right

i did integration by parts twice, but my answer seems wrong still cos i've never seen sin2, cos2 o-o
i got 8sin2 -4cos2 - 4

isn't the answer just 0?

 

[Lukybear]

I think its just 0

 

[hscishard]

I haven't done this kind of stuff yet but...

If it is equal to 0, therefore its an odd function right? x^2 is even, so sinx mst be odd right?
Just asking.3

 

[GUSSSSSSSSSSSSS]

isn't the answer just 0?

mr drongoski, long time no see haha

I would also have to vouch for the answer being 0

if f(x) = (x^2)(sin(x))
f(-x) = ((-x)^2)(sin(-x))
= (x^2)(-sin(x))
= -(x^2)(sin(x))
= -f(x)
and since the limits are equal but opposite in sign, the areas above and below the x axis cancel each other out, leaving a final integral of 0

 

[Drongoski]

oh, hi GUSS . . . . SSS

Long time no see indeed.

 

[fullonoob]

oh yeah its an integration property with odd function :x
i tried to solve it, was pretty lol xD
thx

 

[cutemouse]

The integration of an odd function about symmetrical limits is zero.