valentine_strongrod
Badges: 0
#1
Report Thread starter 11 years ago
#1
Hi

dy/dx = y^2 . ln x

so heres wut i do:

y^-2 dy = lnx dx
-y^-1 = lnx dx...
cept i dont know how to integrate lnx
any tips??
0
reply
Kolya
Badges: 15
#2
Report 11 years ago
#2
See that \ln x = 1 \cdot \ln x and use IBP.
0
reply
kamie
Badges: 1
Rep:
?
#3
Report 11 years ago
#3
by parts, integrate 1.lnx
0
reply
valentine_strongrod
Badges: 0
#4
Report Thread starter 11 years ago
#4
ah thnx dudes...i mean dude and dudette......havent touched C4 for 4 months :P
0
reply
kamie
Badges: 1
Rep:
?
#5
Report 11 years ago
#5
lol i wish, i had it on fri, and it feels like i haven't touched fp1 since easter, which i umm, haven't lol!
0
reply
valentine_strongrod
Badges: 0
#6
Report Thread starter 11 years ago
#6
oh and heey,
Integration by parts = u.v - (integration sign) u. v' ... yeh?
0
reply
valentine_strongrod
Badges: 0
#7
Report Thread starter 11 years ago
#7
(Original post by kamie)
lol i wish, i had it on fri, and it feels like i haven't touched fp1 since easter, which i umm, haven't lol!
u got FP1 too this monday??
0
reply
kamie
Badges: 1
Rep:
?
#8
Report 11 years ago
#8
you'll be integrating x.1/x, i can't figure it out from u's and v's, i learnt words! and yes i have got fp1 on monday, and i can't do first order, second order or polar
0
reply
valentine_strongrod
Badges: 0
#9
Report Thread starter 11 years ago
#9
u know how good i feel hearing that ?
i thought i was the only one in this state of destruction lol..
so i suppose ur doing hard core revision right now eh?


another Qu:
e^-x^2 dy/dx = y.x
0
reply
insparato
Badges: 15
Rep:
?
#10
Report 11 years ago
#10
 \frac{1}{y} \frac{dy}{dx} = xe^{x^2}

Then note that

if  y = e^{x^2}

then

 dy/dx = 2xe^{x^2}

so  \int dy/dx = 2 \int xe^{x^2} = e^{x^2} + C

So what does  \int xe^{x^2} equal?
0
reply
valentine_strongrod
Badges: 0
#11
Report Thread starter 11 years ago
#11
i think ive lost u already...cant take in the ^ and the x's lol
but i think im on the right track now..
0
reply
Chaoslord
Badges: 4
Rep:
?
#12
Report 11 years ago
#12
its

- \int \frac{du}{dx} \times v

thats if your initial is

\int u \times \frac{dv}{dx}

p.s. i hate all FPs =[
0
reply
insparato
Badges: 15
Rep:
?
#13
Report 11 years ago
#13
I've latexed it, but basically im integrating the differentiated function.

You should be looking at

If  2\int xe^{x^2} = e^{x^2} + C

Then you need to divide both sides by a half to get the desired answer to your integral.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • University of Surrey
    Postgraduate Open Afternoon Postgraduate
    Wed, 23 Oct '19
  • University of Bristol
    Undergraduate Open Afternoon Undergraduate
    Wed, 23 Oct '19
  • University of Exeter
    Undergraduate Open Day - Penryn Campus Undergraduate
    Wed, 23 Oct '19

Would you turn to a teacher if you were being bullied?

Yes (53)
25.6%
No (154)
74.4%

Watched Threads

View All