Question

what is the integration of (xcos(x))

Answer 1

Have you heard of integration by parts?

Answer 2

\[\int vdu=uv-\int udv.\]
lol

Answer 3

im a dissenter for no apparent reason; kinda like the jimmy dean kid :)

Answer 4

across, why did you delete yours ? now amistre looks foolish with that "lol" for no reason :)

Answer 5

ohh, i look foolish with or without it. its a trademark

Answer 6

down up
cos(x)
+x sin(x) = x sin(x)
-1 -cos(x) = +cos(x)
+0 -sin(x) = 0

int: x cos(x) dx = x sin(x) + cos(x) + C

Answer 7

to chk:

d/dx: x sin(x) + cos(x)

x' sin(x)+x sin(x)' + cos(x)'

sin(x)+x cos(x) -sin(x) = x cos(x)

Answer 8

i think one day amistre will be an integrating god

Answer 9

To become an integrating god, one must first be able to find an anti-derivative of:\[\int e^{x^{2}}dx.\]:P

Answer 10

i think amistre can do it
lol
i can't so i will never reach goddess status

Answer 11

lol ..... i do that in my sleep, where reality and fantasy collide in an amalgamation of idiocy and genius

Answer 12

i felt like i didn't sleep last night
i dreamed about programming
i dreamed about having problems figuring out my code

Answer 13

That's bad, coz if you worked a lot on it - it's all gone when you wake up (even if you remembered to save your work often).

Answer 14

lol

Answer 15

i worked on it all last night and i don't remember what my brain concluded
because my brain doesn't have a save button :(

Answer 16

@amistre one day i would like you to show me that up down thing. it is what you see in the movie "stand and deliver"

Answer 17

its what you do when you go ride the slides

Answer 18

its just my version of an IBP table:

with multiple integration by parts; you tend to use the same u and v values such that u derives down to 0 and v just integrates up for the ride ....

Answer 19

\[\int udv=uv-(u'\int' v)+(u''\int'' v)-(u'''\int'''v)+(...\]if that makes any sense

Answer 20

yeah i have seen it but i guess i need to write it out for myself. if you ever saw the movie "stand and deliver" escalante does this on the board in like 6 seconds. crosses up and down

Answer 21

ill have to check it out :)

Answer 22

yeah, i tend to bump up the right side so i dont have to diagon it ...

Answer 23

which is why the first row is missing the "u"