BF2S Forums College/University Homework Help Thread v1.0

The Sheriff wrote:

Mek is 20 if not 21, same age as Ted/Uzique

mek is a dropout and a loser and has no place in a HOMEWORK thread.

this is OFFICIAL.

If he'd stayed in uni he'd be in his third year now, he's a year older than me, same age as bennisboiz, I can remember they both started uni at the same time.

Last edited by The Sheriff (2009-10-02 07:41:41)

Bevo wrote:

WldctARCHe wrote:

Bevo wrote:

Anyone know why he crossed that bit out? I used the chain rule and then factored out the 4... don't see anything wrong?

The only reason i could see for him to cross it out would be if lamda is constant because then it wouldn't have a derivative.

If that was true, wouldn't the first half of my equation be wrong?

No the first half is fine.  y'=4(x + lambda)^3 (x^4 + lambda^4) - (x + lambda)^4 (4x^3) is correct.
When you differentiated (x + lambda)^4 you get 4(x + lambda)^3 (1 + 0) = 4(x + lambda)^3. Lambda is a constant so its derivative is 0 which is what you had for the first part but then accidentally included it in the second part.

presidentsheep wrote:

can someone differentiate y=sec(2x) quickly... im tired and bored of maths. Dont need an explanation, just the answer.

http://library.wolfram.com/webMathemati … /WalkD.jsp

Bevo wrote:

Okies, need help differentiating something difficult

http://static.bf2s.com/files/user/19950/3.jpg

thoughts? I think I did it correctly, but when I start substituting the 3pi/4 and pi/2, I end up with square roots that I'm not supposed to have. The final answer is -11/384, but I think I messed up somewhere because those square roots probably won't cancel...

ITS SIDEWAYS

FUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUCCCCCCCCCCCKKKKK

Bevo wrote:

Okies, need help differentiating something difficult

http://static.bf2s.com/files/user/19950/3.jpg

thoughts? I think I did it correctly, but when I start substituting the 3pi/4 and pi/2, I end up with square roots that I'm not supposed to have. The final answer is -11/384, but I think I messed up somewhere because those square roots probably won't cancel...

I want your handwriting please! would help but I took Calculus like a year ago ;\

dude l2wolfram

and you don't do integration by parts when you have sin and cos to some absurd powers, the trick is breaking them up so you can write them in udu form...which it looks like you were doing well Bevo. I am not quite sure you broke it up right, but definitely going in the right direction. I know there is always a trick about whenever sin is raised to an odd power and cos to an even power do x, when both even do y, etc. but I can't remember what it is. Might try to look for that/come up with it yourself though, makes things much more striaghtforward to get some solid general rules.

Flaming_Maniac wrote:

dude l2wolfram

fuckin EiT's @ work all have that bookmarked. after i don't know how many years @ school, they'll howl every time i delete the shortcut and they can't remember how to get it back!

Last edited by burnzz (2009-12-02 19:50:14)

yeah the trick is to break off a single sinx and cosx and use them as the DX and then just set u = sinx or cosx and raise them to a power so you can integrate cleanly. which i did.

but when I start to substitute, it gets ugly.

Flaming_Maniac wrote:

http://www.wolframalpha.com/input/?i=integrate+sin^5%28x%29cos^3%28x%29

I mean if you get that equation by hand christ just write the answer on the next line.

it doesn't work that nicely, and I have no idea why wolfram insists on making everything cosine. the answer is provided in the book, there's no mystery to that, it's about process. we have a limited number of examples worked out because our prof is a 70 year old douche and doesn't like to teach.

Look at the last three lines, those are all the same thing. In the second to last line they just factored it, and I think the last is to make it easier to write as a series.

If you get one of those three lines then you know how to integrate it and you suck at plugging numbers in. That is the work of a calculator. If you can't use a TI-83 or better to do that and/or are not making a stupid mistake right now and you actually are unable to simplify it, then yeah you should work on it. Plugging in numbers to a definite integral can't be the point though.

nukchebi0 wrote:

Nevermind, I think I cheated a step. Still, check the answer with a graphing calculator to ensure the book is correct.

Not doing trig sub before I split doesn't seem to be getting me anywhere... I guess I shall