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Mathematics 19 Online
OpenStudy (wasiqss):

Integral of (e^x)/x

OpenStudy (anonymous):

Applying the Divide rule of Derivative here..

OpenStudy (wasiqss):

lol water do it by that way i will give you thousand medals :P

OpenStudy (wasiqss):

and its integration man~

OpenStudy (anonymous):

Sorry I did not read the question fully..

OpenStudy (anonymous):

\[\large \int\limits\frac{e^{x}}{x} dx\]?? looks like cant be solved by elementary methods..

OpenStudy (wasiqss):

ahaha omni in your dreams do it :P

OpenStudy (anonymous):

We can use here Integration by Parts...

OpenStudy (anonymous):

http://www.wolframalpha.com/input/?i=integrate+%28e^x%29%2Fx like srsly? how can you solve it?

OpenStudy (wasiqss):

hahahah omni i heard you saying i own calculus ? :P

OpenStudy (anonymous):

term by term integration of the infinite series?

OpenStudy (anonymous):

like srsly.. http://en.wikipedia.org/wiki/Exponential_integral

OpenStudy (anonymous):

hi water , have you heard of exp x = \[x + x ^{2}/2! + x ^{3}/3! + x ^{4}/4!.........\]

OpenStudy (anonymous):

Wasi, what calculus are you in

OpenStudy (anonymous):

if you know this then u can substitute exp x by the above and further see if its solvable !

OpenStudy (wasiqss):

keep thinking :P

OpenStudy (wasiqss):

hint it can be done by parts

OpenStudy (anonymous):

i know it can be done by parts however are you in calculus 2

OpenStudy (wasiqss):

well outkas do it by parts i wanna see

OpenStudy (anonymous):

For convenience, 1/x is the first function.. e^x as second function.. \[\int\limits_{}^{}(\frac{1}{x}).e^x.dx = \frac{1}{x}.e^x - \int\limits_{}^{}(\frac{-1}{x^2}.e^x).dx\] \[= \frac{e^x}{x} +\int\limits_{}^{} \frac{e^x}{x^2}.dx\] But now x will move on increasing like x^3, x^4 etc etc..

OpenStudy (wasiqss):

yeah now you have to do integration of (e^x)/x^2 right?

OpenStudy (anonymous):

yes however switch the u and dv to go back and then add them and divide by 2

OpenStudy (anonymous):

Right but that will lead to x^3 then this process continues..

OpenStudy (anonymous):

in otherword let dv = -1/x^2

OpenStudy (wasiqss):

haha outkas right :D :D

OpenStudy (anonymous):

then add the integrals and divide by 2

OpenStudy (wasiqss):

it is a two step integral

OpenStudy (wasiqss):

@Omniscience poor you :P

OpenStudy (wasiqss):

outkas which calculus you doing

OpenStudy (anonymous):

I'm don with calculus, I'm in Differential Equations right now

OpenStudy (wasiqss):

im good at D.E's :D

OpenStudy (anonymous):

however i don't remember hardly anything from calc 3.. and i wouldn't remember the series i it weren't for review

OpenStudy (wasiqss):

calc 3 sucks!

OpenStudy (anonymous):

indeed it does

OpenStudy (wasiqss):

D.E are real good, in which uni you are and which year?

OpenStudy (anonymous):

nothing like drawing 3d objects on a 2d piece of paper

OpenStudy (anonymous):

i'm a at a community and it's around my second/3rd year

OpenStudy (wasiqss):

i just cleared the first year only :/

OpenStudy (wasiqss):

now i will go to second

OpenStudy (anonymous):

good try mukushla :)

OpenStudy (anonymous):

tnx

OpenStudy (anonymous):

there was a little mistake in my answer \[\int\limits \frac{e^x}{x}dx=\int\limits \frac{1}{x} \sum_{n=0}^{\infty} \frac{x^n}{n!}dx=\sum_{n=0}^{\infty} \int\limits \frac{x^{n-1}}{n!} dx=\ln x+\sum_{n=1}^{\infty} \frac{x^{n}}{n.n!}\]

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