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| My turn to ask for maths help | |
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| Tweet Topic Started: Mar 6 2008, 12:33 PM (310 Views) | |
| ***musical princess*** | Mar 6 2008, 12:33 PM Post #1 |
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HOLY CARP!!!
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I was given a homogenous equation in which i am trying to put y' in a general form of y; i have subbed in xv for y and done loads of rearranging to get it into a separable form. I know i have done it right up to this bit, but now that i am trying to integrate, i'm stumped. I've got... Int.[(1-v)/(1+v^2)]dv = Int.[dx/x] I've got the right hand side. It's just... ln|x|+A ... but how the fook do i go about integrating the left hand side.... [(1-v)/(1+v^2)]dv ??? Anyone...??? x |
| x Caroline x | |
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| Renauda | Mar 6 2008, 12:38 PM Post #2 |
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HOLY CARP!!!
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have you considered 2% or 1% skim rather than homogenized? |
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| ***musical princess*** | Mar 6 2008, 12:40 PM Post #3 |
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HOLY CARP!!!
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That didn't work out too well either ( :rolleyes: :lol: ) x |
| x Caroline x | |
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| Klaus | Mar 6 2008, 12:42 PM Post #4 |
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HOLY CARP!!!
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Can you post the full exercise? I have no idea what "a homogenous equation in which i am trying to put y' in a general form of y" means. Is all you want to know the integral of (1-v)/(1+v^2) ? |
| Trifonov Fleisher Klaus Sokolov Zimmerman | |
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| ***musical princess*** | Mar 6 2008, 12:43 PM Post #5 |
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HOLY CARP!!!
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Yep, i've done the rest. All i need to know is how i intergrate that so i can finish the question x |
| x Caroline x | |
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| ***musical princess*** | Mar 6 2008, 12:45 PM Post #6 |
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HOLY CARP!!!
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The question i'm doing is:- Find the general solution of the equation (x-y)y'=(x+y). x |
| x Caroline x | |
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| Klaus | Mar 6 2008, 12:46 PM Post #7 |
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HOLY CARP!!!
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Is it possible that your derivation of (1-v)/(1+v^2) was wrong and what you really need is (1-v)/(1-v^2) ? Because the latter would be quite easy to solve, whereas I'd guess that the former has no analytical solution but only a numerical one. |
| Trifonov Fleisher Klaus Sokolov Zimmerman | |
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| Klaus | Mar 6 2008, 12:48 PM Post #8 |
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HOLY CARP!!!
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What is y'? Some kind of derivation? But of which function, and at which coordinate? |
| Trifonov Fleisher Klaus Sokolov Zimmerman | |
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| ***musical princess*** | Mar 6 2008, 12:48 PM Post #9 |
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HOLY CARP!!!
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Nope, it's definitely an addition sign. Believe me, i checked for that very thing about 30 times lol x |
| x Caroline x | |
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| Klaus | Mar 6 2008, 12:51 PM Post #10 |
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HOLY CARP!!!
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I have still no idea what the goal of this exercise is. Here is a solution: x=0, y=0, y'=0. Equation holds. This is probably not what the teacher wants, but your (or the teacher's) description is very underspecified. |
| Trifonov Fleisher Klaus Sokolov Zimmerman | |
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| ***musical princess*** | Mar 6 2008, 12:53 PM Post #11 |
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HOLY CARP!!!
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y' (or y-prime) is just a short hand version of dy/dx. It's the differential of the function of y with respect to x. What the question is asking is for me to find what the original function is basically. So they want it written as y(x)=... The way to do it is to substitute y for xv(x). So the original question becomes... dy/dx=(x+y)/(x-y) Which when you substitute becomes... v+xv'=(x+xv)/(x-xv) Which, when you take out a factor of x, separate the variables and rearrange, becomes... (1-v)/(1+v^2)dv=dx/x x |
| x Caroline x | |
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| sarah_blueparrot | Mar 6 2008, 01:14 PM Post #12 |
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Fulla-Carp
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That's easy. The answer's 15. |
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Death is simply a shedding of the physical body like the butterfly shedding its cocoon. It is a transition to a higher state of consciousness where you continue to perceive, to understand, to laugh, and to be able to grow. - Dr. Elizabeth Kubler-Ross | |
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| ***musical princess*** | Mar 6 2008, 01:16 PM Post #13 |
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HOLY CARP!!!
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or 42 ![]() x |
| x Caroline x | |
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| JBryan | Mar 6 2008, 01:18 PM Post #14 |
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I am the grey one
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Have you tried integration by parts? I am too busy right now to try and work out whether it would work on this but I know it has been useful to me in the past on problems like this. |
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"Any man who would make an X rated movie should be forced to take his daughter to see it". - John Wayne There is a line we cross when we go from "I will believe it when I see it" to "I will see it when I believe it". Henry II: I marvel at you after all these years. Still like a democratic drawbridge: going down for everybody. Eleanor: At my age there's not much traffic anymore. From The Lion in Winter. | |
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| ***musical princess*** | Mar 6 2008, 01:20 PM Post #15 |
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HOLY CARP!!!
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Oh you legend JB, i think that might actually work... i never thought about that what with it being a quotient but i'll just set dv as (1+v^2)^-1. I'll give it a try... x |
| x Caroline x | |
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| ***musical princess*** | Mar 6 2008, 01:55 PM Post #16 |
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HOLY CARP!!!
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It didn't work.... The sub integral just getting a bigger and bigger degree of v so it's was a constant product integration ![]() x |
| x Caroline x | |
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| Klaus | Mar 6 2008, 02:36 PM Post #17 |
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HOLY CARP!!!
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Int.[(1-v)/(1+v^2)]dv = arctan(v) - 1/2 log(v^2+1) |
| Trifonov Fleisher Klaus Sokolov Zimmerman | |
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| ***musical princess*** | Mar 6 2008, 02:45 PM Post #18 |
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HOLY CARP!!!
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Oooh... how did you do that? x |
| x Caroline x | |
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| Klaus | Mar 6 2008, 02:59 PM Post #19 |
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HOLY CARP!!!
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Int.[(1-v)/(1+v^2)]dv = Int.[1/(1+v^2)]dv - Int.[v/(1+v^2)]dv = arctan(v) - 1/2 log(1+v^2) |
| Trifonov Fleisher Klaus Sokolov Zimmerman | |
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| Klaus | Mar 6 2008, 03:07 PM Post #20 |
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HOLY CARP!!!
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What kind of course is this, MP? High school maths? Or something else? |
| Trifonov Fleisher Klaus Sokolov Zimmerman | |
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| JBryan | Mar 6 2008, 06:31 PM Post #21 |
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I am the grey one
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I was entertaining multiplying by (1 - v)/(1 - v) but I didn't really have the time to work on it. I have a life, you know.
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"Any man who would make an X rated movie should be forced to take his daughter to see it". - John Wayne There is a line we cross when we go from "I will believe it when I see it" to "I will see it when I believe it". Henry II: I marvel at you after all these years. Still like a democratic drawbridge: going down for everybody. Eleanor: At my age there's not much traffic anymore. From The Lion in Winter. | |
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| ***musical princess*** | Mar 7 2008, 04:34 AM Post #22 |
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HOLY CARP!!!
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Degree (Bsc) - uni x |
| x Caroline x | |
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