Topic awaiting preservation: Math Help For Integrally Challendged Biology Student... (Page 1 of 1)

Hey guys,
I'm currently studying for a math exam (tomorrow), and well, most of the training problems went pretty smooth, but there are two integrals I just can't solve.
Maybe you can help me and show me how to solve them?

Problem a)
Int(1 to 2, x^3 * ln(x) dx)
I guess I have to use substitution followed by partial integration... but it doesn't seem to work quite that easily..

Problem b)
Int(0 to 1, e^x * sin(e^x - 4711) dx)
I'm 100% lost on that one...
Help! Pretty Please!

thanks,

Tyberius Prime

It was sometime ago now (2 months)...
But I think that you have to look what ln(x) is when intergrated.
that's all I remember.

I was good at it some more than 15 years ago...
Now, it's not in my recollection anymore (does this remember you of any USA President... "it's not in my recollection...")

The poster has demanded we remove all his contributions, less he takes legal action.
We have done so.
Now Tyberius Prime expects him to start complaining that we removed his 'free speech' since this message will replace all of his posts, past and future.
Don't follow his example - seek real life help first.

Damnit, I tried to finish this but I dont have the time, go here http://www.sosmath.com/calculus/integration/byparts/byparts.html

I vaguely remember seeing problem b in the past. If it's the same as what I remember, then to solve it, you must perform the same technique on it twice in a row (I think it's integration by parts, not sure though). After doing that, you should get something like

(blah blah blah) - Int(0 to 1, e^x * sin(e^x - 4711) dx)

Where the second half (after the - sign) is the same as what you originally had. Then you set it equal to what you originally had (since it *is* equal to what you started with, that's how you arrived at it), so you have:

Int(0 to 1, e^x * sin(e^x - 4711) dx) = (blah blah blah) - Int(0 to 1, e^x * sin(e^x - 4711) dx)

which is equivalent to

2 * Int(0 to 1, e^x * sin(e^x - 4711) dx) = (blah blah blah)
Int(0 to 1, e^x * sin(e^x - 4711) dx) = (blah blah blah)/2

so (blah blah blah)/2 is the solution.

For problem a, do integration by parts but instead of substituting dv= ln(x),
set u = ln(x)
dv = x^3 dx.

It was easy after that.

Bees in the what now

I don';t know if it's possible, but I'm more lost than Dufty...I didn't even pick up the bees.

Looks like Slime and beaner got it. After going through both of them I'm pretty sure I got it right, but I had more fun just doing them. I'd forgotten how much fun Calc is.

.sssss

http://www.hostmysig.com/data/tornshoulder/shoulder.jpg

Shoulder...you need to put that url into an tag, not a tag if you want it to show up as an image rather than a link to an image.

Please, for the love of everything holy, keep it as a url..

*shudder*

[This message has been edited by Raptor (edited 02-19-2003).]

hehehe...

thank y'all!