Topic: Integration/Integrals? (Calculus I) (Read 814 times)

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I'm just curious if someone could give a a quick (or not-so-quick, whatever) rundown on integrals. I.e. what they are, what the notation is, what they stand for, etc.
I understand derivatives but I'm trying to see where this whole integral thing is going.
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Dude this is pretty integral to calculus..
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uuh is this a joke?

if not it's very broad. integrals are the opposite of derivatives...

for a function f(x),

the derivative of f(x) = f'(x),

the integral of f'(x) = f(x)
sometimes, you need to quote yourself to feel important.
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Yes I surmised that much. But I mean what is unique to integrals? Do they have their own sets of rules? What do they mean (i.e. like differentials are the instantaneous rate of change), what are the different types of notation, etc.?
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the wiki on integration is pretty clear about it all

at its most basic it's the area under the curve on a given interval if it's definite or the antiderivative if it's indefinite
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i'm sure you could piece together some bits of information for random posts in this topic and eventually figure out some tings about integrals, but why would you think this spattering of information would be any better than googling "how to integrate" or "basics of integration" or "calculus help" or something?
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If you really think the world can be reduced to numbers then you've got bigger problems buddy. This is 2009, hear of a little thing called 'post modernism?'

Maybe do a little rational thinking rather than rational equation solving in that brain of yours.
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The best explanation I could give in words is that if you know the rate of change of [some ][/some] across [some ][/some], the integral of that rate would give you the actual value of that variable at whatever point you want.

So like, if you had the graph of velocity (rate at which the position is changing at a point in time), the integral of that graph would give you the position at any point in time.

It's pretty hard to grasp at first (definitely more so than derivatives at least) but as you do more of them it'll click.

As far as integration rules go, depending on the function, it could either be straightforward or a real bitch. The kx^(k-1) rule is easy enough to reverse, but when you've got a chain rule situation, it gets to be a pain in the ass real quick.
Last Edit: March 03, 2009, 01:30:44 am by Sredni Vashtar
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I like derivatives, and using all the rules. I just got done a taking a test on them today. Try looking up how to compute integers using the calc. I use a TI-89.

http://www.humboldt.edu/~eb38/math110/integral89.html
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yeah it's so difficult to compute them using a calculator specifically made for that

have they banned the use of ti-89s on the ap exam yet? they should
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its like tic tac toe

tabular integration
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on that TI-89 page it says "Hence,  integral of (4x 4 + 3x)dx = (4/5)x 5 + 3x + c."

lol they integrated wrong!
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also the TI-84 (and TI-83, I believe) can do definite integrals so yeah


AP calc can be somewhat of a breeze with those but esp with that 89. it should be banned
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on that TI-89 page it says "Hence,  integral of (4x 4 + 3x)dx = (4/5)x 5 + 3x + c."

lol they integrated wrong!
no, they just typed an extra x
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oh i just saw the picture there. trueeeee.
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area under the curve,, duh
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fuck esiann already said that
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They can also be used for calculating various other sums and other hardcore shit. Volumes for example, or the sum of some quantity along a path (say, you cycle through a cloud of mosquitoes. If you know how they are distributed in the cloud and know your path through the cloud, you can integrate the sum of how many of them you'll catch in your mouth). I have very little idea how, just heard the big boys talk about it one day. Areas are definitely the most common and intuitive application though, just showing off here.
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Integrals are essentially used to get areas under curves.

If you've done Reimann sums yet, you know that you can cut sections of the curve into a bunch of rectangles, multiply the bases (Delta X) together with the heights (Y values), and approximate the area under the curve. Well with integrals, you do the same thing, except the you take the limit of Delta X as it approaches zero (turning it into dx: a very, very small distance). This time though, the area under the curve is (practically) exact.

There are three parts to the basic integral. That fatass "S" thing in front is known as Sigma, and basically tells you to add. Following that, there's the f(x) equation (the "height" of the rectangles). Finally, there's dx (the infinitesmally small "width" of the rectangles). So the Sigma up in front tells you to add all the little areas of dx*f(x) together.

It might sound convoluted at first, but it'll eventually click. You're going to really love calc II next year, when they try to tell you that 1 the the infinite power is fricking 2.718. Now THAT'S convoluted. (1x1x1x1x1x1... = ...2?)

As for integral applications, you'll eventually use them to figure out how long curves actually are, or to find a path equation for an electron in particle physics. Pretty much every physical science field uses integrals in some way or another. They're pretty integral (AHAHAHAHAHAha...ha...haah...) to physics jobs.
Last Edit: March 06, 2009, 03:06:28 am by Juris
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