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johnlopez 5:18 pm March 21, 2010
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I found that its easier to not memorize the LIATE rule. When I do u-sub, I pick my U so that it gets smaller when you take the anti-derivative. By just looking at the problem, you can tell what is the proper way to do u-sub if you just try to look at it by what makes the U get smaller, or even just drop out.
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davidbnorris 9:31 pm March 4, 2010
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Also, I don't know if this was mentioned but for the LIATE rule how you decide what to do is if the term you are using is closer to L than it shoul be U and if it is closer to E is should be DV
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davidbnorris 9:28 pm March 4, 2010
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I also have trouble with the homework. I have trouble understanding what specifically the author is asking about and some of the problems have no examples in the chapter. It makes you think really hard about the question but sometimes thats a good thing
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jonharris 8:06 pm March 1, 2010
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I have something that is similar to your approach, which helps when it comes to specifying what u and dv are in a problem that involves integreation by parts.
The approach that my tutor told me to take is LIATE
L: Logs
I: Inverse Trig
A: Algebraic
T: Trig
E: Exponential
THis is very similar to what you had, and it was a major benefit when i approached integration by parts.
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bwong 12:43 am March 1, 2010
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I have the same problem as everyone here. I understand in class and when it comes to the homework, i'm screwed. The last homework we did, it really did take like 30+mins to get through each problem, and that's just the ones I could do on my own. I do not know when i should use U-sub or when to integrate by parts. But every homework, i've had help from a friend. He mentioned LIPET for all integration by parts. I don't know if it always helps, but it should on most problems.
for those who don't know it: LIPET is the order of things you wanna use as "u", for example, L stands for log, so you want to take a log expression out of the intergral for "u" and go from there
L – logs
I – inverse trig functions
P – polynomails
E – exponentials
T – trig
Now, LIPET may help but I don't know if it works all the time, so don't always focus so much on it. I hope this helps some of you.
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chasemcquarrie 12:47 am February 26, 2010
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Personally, I struggle with which technique to use when integrating. I have trouble distinguishing when to use U substitution and when to integrate by parts. I just need to practice a bunch of problems and hopefully gain some insight for making those decisions.
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sausenk-10 12:04 am February 26, 2010
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I feel the same way. I understand everything in class and it all seems very logical. However, I doubt that I can look at a problem and know how to solve it without the book or my notes to reference. I guess what I am saying is that I sometimes get confused on how to start a problem, and I hope that doesnt happen on the test. Oh, and on another note, I think that "wake up alert" hypnosis worked today. Pretty legit.
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hectorramos 1:44 pm February 24, 2010
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My problem in the class is that I completely understand the lecture, but once I start the homework I freeze and end up putting it off till the last minute, as I am doing right now, but anyways I get confused when to use U-substitution and when to integrate by parts. On the HW due today I seriously did not use U-substitution at all, but rather tried to integrate by parts through every problem. I use trial and error methods and almost always end up with errors but as I integrate by parts I tend to use the function that is easier to integrate as my "dv" and work with deriving the other function as my "u"…but like I said, I'm almost always incorrect, is there a better way to go about these problems aside from starting them earlier and heading to Doc for help??
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jonharris 8:03 pm February 22, 2010
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What about when you have something like e^4x or something of that nature?
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johnlopez 3:09 pm February 22, 2010
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To help with the setting the right elements to "u" and "v", look at the formula. If it is the integral of udv, then set the element before the "dv" part as u and then have v as 1. However, with trigonometric identity problems, I think it depends more upon the equation that one specific explanation, but I could be wrong about that.
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rossjohn06 7:18 pm February 18, 2010
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I have a problem figuring out what I should set "u" or "v" in the problems and sometimes it can get very confusing when it seems like I've integrated way too many times.
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