Question

need help with an indefinite integral

Answer 1

i need to practice on integrals so i'll help :P

Answer 2

can someone explain how\[\int\limits_{?}^{?}1/\theta^2 \cos(1/\theta)d \theta becomes -\sin(1/\theta)+c\]

Answer 3

I couldn't find the integral symbol without bounds so I just put them blank

Answer 4

lol you just have to erase the ? anyway.... let me try to fix this....

\(\large \int \frac{1}{\theta ^2} \cos (\frac {1}{\theta} ) d \theta = -\sin (\frac{1}{\theta} ) + C \)

that's the question correct?

Answer 5

\[\int \frac{\cos(\frac{1}{\theta})}{\theta^2}d\theta\]

Answer 6

i will be quiet, just wanted to write it

Answer 7

the one that igbasallote posted

Answer 8

lol ok

Answer 9

lol

Answer 10

well then i'll give you a hint...

let u = \(\large \frac{1}{\theta}\)
du = \( \large \theta ^{-1} = -1(\theta ^{-2}) = - \frac{1}{\theta ^2}\)

can you see how to do it now?

Answer 11

:O @Zarkon you're mod too??? wow congrats!

Answer 12

ty

Answer 13

@Zarkon congrats on being a mod. damn everyone but me? jealous

Answer 14

what is mod?

Answer 15

maybe in the next draft pick

Answer 16

haha lol yeah satellite i noticed too =)) you deserve to be one after all your contributions to this site ^_^

Answer 17

@chrisplusian mods are moderators kind of the ones who overlook the site..global moderators have great prestige because it means they are the best in their subject...anyway back to your question :D

Answer 18

you guys/ girls are awesome. I can't find help at my $240 a credit hour school so I come here:)

Answer 19

do you know how to go from that substitution @chrisplusian ?

Answer 20

yes i have it. because du is one over theta squared, d theta. and when I differentiate theta to the negative first it becomes one over d thaeta squared times d theta. I would have never seen that on my own. Thanks

Answer 21

@satellite73 maybe :)

Answer 22

it just takes practice :DDD just remember that when substituting..ALWAYS substitute the more complicated one

Answer 23

probably doesn't help that i am still trying to stay relatively anonymous

Answer 24

what makes it more complicated? the fact that it is the argument of a trig function?

Answer 25

yup :DD

Answer 26

by the way...i think the frontrunners for the next mod picking is satellite and hero..well i think they're the most deserving ones haha