# BobbyJoeCool

Senior Members

535

1. ## limit question, confusing

sorry, double post... the one below is correct (pressed wrong button). If a mod would delete this, that would be nice of them!
2. ## Anti-Derivative

Yea, I remember now... this was like a week before graduation, and everyone had one foot out the door...
3. ## Anti-Derivative

that looks farmiliar, but... I can't remember if we did that in Intro to Calc in High School... can you give me a basic idea of how do get... $\int_{0}^{1} x^2 \, dx = \tfrac{1}{3}$ Just to see if it jogs a memory of it? Much faster than counting squares (especially if you want an exact answer on a curve and hsve to use limits!)
4. ## Math Competition

And over in France, college is your senior year of high school, and university is college... (those silly French?)
5. ## Math Competition

I still have a couple tests from my high school Iowa State Math Competition (and a power question or two). Would you be interested in those? I mean, part of the thing about those were that you have a time limit on you, but still, they're some.... interesting questions... And I don't know the answers, but I have the questions. EDIT:And some questions are a "you have no calculator" question...
6. ## limit question, confusing

oh... right. Limit derivaitve. that would be moderatly difficult...
7. ## Planetary allignment

Why is is that most of the planets of the solar system all lie pretty close to a plane? Is there something special about it? Sorry for sounding stupid...
8. ## SFN Frapper

There ain't been a good lynchin' since 19 ought 6!
9. ## limit question, confusing

the derivitive of sin(x)=cos(x)...
10. ## MORE related rates of EVIL!!!!

Extra Credit on the test (already taken)... Here's the question: You have a 5 meter long trough. A cross section of the trough is an isololes trapazoid with upper base 3 meters, lower base 2 meters and an altitude of 2 meters. You are pouring water into the trough at a rate of 1 cubic meter per second. What is the rate of change of the height of the water at a height of .5 meters... here is what I got out for givens and the variable I need to solve for... V'=1 l=5 b1=2 h=.5 h'=? $V=\tfrac{b_{1}+b_{2}}{2} \cdot h \cdot l$ b1 is 2, l=5, but I can't figure out b2! Then it's a simple matter of related rates, and diferentiate with respect to t... $V'=\tfrac{2+b_{2}}{2}\cdot 5 \cdot h'$ $1=\tfrac{2+b_{2}}{2}\cdot 5 \cdot h'$ $h'=\frac{1}{\tfrac{2+b_{2}}{2}\cdot 5}$ $h'=\frac{2}{5(2+b_{2})}$ SO I'm this close, but can't figure out this b2 (which is probably something simple... and I just can't think... It's been too long since Geometry) Can someone help me out (like pointing me in the right direction)?
11. ## Anti-Derivative

He he... does it have to do with x^0=1, and d1/dx=0 and x^-1 cannot be 0? As you haven't dealt with intrigals before... just think of derivitive, but backwards... since it's a simple f(x)=2x... to take the derivative of a function (power rule), you multiply by the exponent, and subtract one from the exponent... to take the "anti-derivative.." go backwards... add one to the exponent, then divide by the exponent... so, general case... $f(x)=ax^n$ $\int ax^n \, dx=\tfrac{ax^{n+1}}{n+1}$ But remember... the derivative of ANY constant is 0... so when taking the intrigal.. you have to add c, where c is any constant... so... $\int ax^n \, dx=\tfrac{ax^{n+1}}{n+1}+c$ the easy way to check to see if you did an intrigal correctly... take the derivative!!! with your example... $\int 2x^1 \, dx=\tfrac{2x^{1+1}}{1+1}+c$ $\int 2x \, dx=\tfrac{2x^{2}}{2}+c$ $\int 2x \, dx=x^{2}+c$ Take the derivative to check your answer... $x^2+c$ $\tfrac{d}{dx}x^2+c$ $2x+0$
12. ## SFN Frapper

And it shows my Zip code as being a town called Bremer, which, by the way, is a PART of my post office, but since Bremer has a population of 8... that's right, it's an intersection with a bar, when the town I live in (Waverly, about 5 miles south of Bremer, which is where the arrow points if you zoom in far enough) is about 8,800 (in 2000) and growing. But yea... My boss lives in Bremer! So I guess I can be her instead!
13. ## Natural Gas

true... I should have known that too... but still... with the vents above it running full boar, I doubt there was any real danger...
14. ## Inside a black hole - what would it be like?

In theory, you could escape from a black hole... you just need to be 2 dimentions, and have no mass (and thus Gravety has no effect on you...) Just good luck making yourself 2D and living....
15. ## Natural Gas

yea, well... I could find the leak (because I could feel it, and hear it). It wasn't a problem. I thought you meant find ratio in the air with the dishsoap, and I'm like huh? but the whole point is, gas (and most things for that matter) don't explode unless they are compressed and REALLY "want" to expand, and fast.
16. ## Natural Gas

Check it out how with dish soap and water? Check to see if (where) it's leaking?
17. ## Related Rates of EVIL!!!

and as I realize that one od my questions got cut off... how did it get dr/dt and dh/dt? In other words, how do you get from the second to last line of latex, to the last?
18. ## Natural Gas

Under what conditions is Natural Gas exposive... Say, a room, with exceptional ventalation (a system designed to keep smoke and soot out of the room from a flaming system). The reason I ask: there was a gas leak at work, you could smell it (strongly) pretty much within 4 ft of the gas pipe, and nothing anywhere else. And, we have an open flame broiler. And there was a mild amount of panic involved... And I was trying to tell people that gas is only explosive in compressed pockets, and with the vents running, it wasn't getting anywhere... So the question... as I right, or just a little intoxicated by the gas. Thanks.
19. ## limit question, confusing

I'm in calc 1... have we haven't "learned" that rule yet (although I know it because my teacher decided to give us a problem I have posted in another thread somewhere). But that makes sence now... thanks!
20. ## Related Rates of EVIL!!!

OK... I was sick and missed this class (Damn my luck!). And the book is no help figuring it out. Related Rates. here's the example problem... Volume of a cone... $V=\frac{\pi r^2 h}{3}$ it's talking about how if a conical tank of water is being drained... it's all a funtion of t,r,h and V... and it says to implicitly diferentiate... $\frac{d}{dt}V=\frac{d}{dt}(\frac{\pi r^2 h}{3})$ $\frac{dV}{dt}=\frac{\pi}{3} (r^2\frac{dh}{dt}+2rh\frac{dr}{dt})$ and then it says that you can see that t is related to r and h! I am REALLY confused.... first off, to that last form... and where is the t? Since the rest of the section is just like this stuff (and I have a test tuesday over this...), I could use a little help! PS... in LaTeX... how can you a)get the fractions smaller ( so that my dy/dx or pi/3 would be the same size as the rest) b)get the parentesis bigger (so that when I paranthesize my big fractions, it reaches from the top to the bottom...)?
21. ## limit question, confusing

ok, so explain this to me... when manipulating a formula for a limit, you can say sin(x)/x=1? becase is you take the limit with sin(x)/x, you get sin(0)/0. sin(0)=0, so it's 0/0. But when did we learn that you use different rules when manipulating the formula for taking a limit?
22. ## limit question, confusing

at the risk of sounding INCREDIBLY stupid... since when was sin(x)/x=1? Because then you mulitply both sides by x, and then sin(x)=x!!!
23. ## Fwargh.

Phi and Glider and them are right... By engaging in a mental or physical battle with anyone, you're mearly sinking to their level. When someone insults me, I laugh at their immaturity. When someone tries to pick a fight with me, I walk away. When someone is trying to outsmart me, I usually don't care (usually, when this is the case, I end up learning something anyway). Etc... Your life, chose to spend it in your own fashion. Now, this guy is rubbing it in your face... he's better than you. No, he's not. Prove you're better than him. Seriously. It will annoy him more if you ignore him, and his insults/pushing things in your face than anything you say. He wants to engage you in a battle of words, don't let him. Play on your field, by your rules, not his.

25. ## Happy October!

I'm twenty... it's not legal, except under the supervision of my parent or guardian in my place of residence... (aka, if I'm at home, the police can't do thing one about it, as long as I'm not violating some other law that would bring down the wrath of the law...). At any rate... I don't drink beer, Vodka + Vermuth. "shaken not stirred." JK... although I have had martinies before... but Bloody Marys have been my friend this month...
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