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abstrusemortal
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26 Nov 2007, 11:31 pm

lau wrote:
abstrusemortal wrote:
lau wrote:

.....

Conversely, a similar expression, "(1+X/N)^N", as N tends to infinity, is much more interesting.



(1+X/N)^N=e^x. That equation is used in a lot of places.

Interesting thought... in your equation, can you give an idea of what the graph of "X" against "x" might look like? (For various values of N)

:)


didn't mean to confuse, I omit some details when I think they're so obvious - I meant to put:

lim (1+x/N)^N = e^x
n-->infinity

it can be proved with L'Hopital's rule or you can do what you did with the graph and see the relationship between the function

f(x) = lim (1+x/N)^N
n-->infinity

and e^x

either way the equation is neat :D


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abstrusemortal
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26 Nov 2007, 11:39 pm

Angelus-Mortis wrote:
Prot wrote:
Quote:
I agree with what you say. People do tend to do that, hence, I always just never really socialized. People picked on me, and I just left them alone and did my own thing.

I can't stand the thought of "watering down" maths. I am a logical person, so to me numbers are the law. Numbers are truth/ To say that 2 + 2 = 5 (for example) gets half points is wrong. I saw a special on math awhile back and the reporters did a study on how kids learn it, and they found that there are ways to improve the learning of maths, but the teachers don't do it, so I think it's more teacher teaching it wrongly than anything else. If they taught it right, there would be no need to water it down. *sigh* Some teachers are brilliant, but we also must admit that some are not good. The not so good ones are where we get the expression: Those that can't do, teach. I think we should try to get teachers to teach it better. Smile But how to do that?

I guess no one can figure out my puzzle in the my earlier post in this thread. Razz It's a hard one.


I think it's has more to do with the way they teach it. The way math is taught now is simply teaching how to apply procedures. Calculus has a lot of procedures that if one follows diligently would allow you to pass the course without needing to gain any understanding of why the procedures and formulas are the way they are. But then, why should I really care about reinventing the mathematical wheel once I gleaned enough of a general idea on how something works like a math formula or procedure for instance? It took some math genius years to come up with the proof in the first place. It's the same reason why I use my calculator for large numbers instead of grinding out the numbers in my head. Once you get the general idea of how something works you can use technology to do the rote procedure executions for you, unless you are on some sort of ego trip. Note, I passed advanced calculus so it isn't as if I'm ranting out of envy or bitterness.


That depends on which calculus course you take. Some of them are more rigorous on understanding and will test you by asking proving questions. If you want my opinion of it, I prefer courses that have an equal compromise between computations and proving (the understanding bit). Besides, if you understand it, you have no need to memorize it; you will know it simply by deriving it. Of course, for a test situation, you might not have time to derive the equations again, and might be forced to memorize it. It might be more accurate to say that you might only use calculators for calculations that are difficult to do in your head. Because 4000000 is a huge number, but multiplying it by another huge number with about the same number of zeroes is not really all that difficult, and shouldn't require a calculator, anymore than you need a calculator to know what 1+1 is. I sincerely despise using a calculator because it makes you rely on it too much. You might encounter a question you don't know how to answer because you don't know how to solve it, and no calculator in the world could help you do that. If you rely on a calculator too much, you might start to believe that you couldn't solve the problem because your calculator wasn't good enough.

Case in point? Consider trying to figure out whether or not 3^5555 + 5^3333 is divisible by 7. If you rely on the calculator too much, you'll punch in the numbers and divide it by 7 to see if you get a decimal point. Then your pocket calculator, having only a maximum of 8 digits, doesn't process such large numbers. So you believe you need a better calculator. But if you don't rely on the calculator, you soon realize that 3^6-1 is divisible by 7, and 3 to any power divisible by 6 divided by 7 always results in a remainder of one (this requires use of the mod concept, but once you understand it, it's not usually difficult to apply), and since 3^5555 = (3^6*925)(3^5), the remainder of 3^5555 when divided by 7 is 1*5 = 5. Continuing in this fashion, you can easily figure out what the remainder is for 5^3333, add the two remainders, and see if you get 7. Which proves that you don't need a calculator to do this kind of question. And for the record, no, I did not use a calculator to figure out whether or not 6 divides 5555 or what the number closest to it was. This kind of mental math can be done quite easily in your head, although I'm not saying this to toot my horn; I'm saying this because it is possible. I am not a human calculator. There are people out there even more extraordinary than myself at that. I know a few of them.

Of course, I consistently like to prove my point by taking my math tests (some of which allow pocket calculators) without any calculators, and do some of the longer or bigger calculations by hand, which isn't much anyways, and complete the test before the end of the period, and get a relatively high score on it--proof that even if we are allowed to use a calculator for a test that might be designed for such purposes, you need not have one to ace it.

You might also be interested to know that most professors or teachers won't dock marks if you don't arrive at a completely refined answer. 32*468 is as good an answer as 14976.


I agree


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Ahaseurus2000
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27 Nov 2007, 2:00 am

I just went over your replies since I last posted, and it boggles my brain so much that all I can say is:


8O 8O 8O :? 8O :? 8O :? 8O 8O 8O :? 8O :? :? 8O
8O :? :? :? 8O :? 8O :? 8O :? :? :? 8O :? 8O :?
8O 8O 8O :? 8O :? 8O :? 8O :? :? :? 8O 8O :? :?
8O :? :? :? 8O :? 8O :? 8O :? :? :? 8O :? 8O :?
8O :? :? :? 8O 8O 8O :? 8O 8O 8O :? 8O :? :? 8O

Now in my original equation:

X^Y - (X - 1)^Y = ?

I commonly think of X and Y when using general Algebra. In this case I was thinking of Natural Integers: {1, 2, 3... }

Another way to write the equation, drawing on quadratic expressions from maths class as I recall them being taught:

X^Y - (X - 1)^Y - ? = 0

I encountered issues when ( -1 =< Y =< 1 ) meaning when Y is any value from -1 to 1 including -1 and 1.


I forgot the equation could be graphed! I wonder if a Z value could be introduced somehow, could the expression graph in 3 dimensions?

:idea: how about:

( X^Y - (X - 1)^Y )^Z = ( ? )^Z

... :lol:



lau
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27 Nov 2007, 12:14 pm

I'm not sure what you wanted from "( X^Y - (X - 1)^Y )^Z = ( ? )^Z", as the Z adds nothing.

Anyway... does anyone know how to trim off the singularities in a Maxima plot3d?

Image


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JasonWilkes
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02 Dec 2007, 1:31 am

Quote:
I would like to think that math shouldn't be about memorizing, but more about understanding it. And this is why I prefer it to dry subjects like history or some sciences. If you can understand how a math proof or theorem works, you simply don't have to memorize it--it will come to you when you go through the proof or theorem again.

However, you usually don't have time to do this on a test, so you might end up memorizing the proofs or their results so that you can solve the problems, but by the time you get around to doing the test, you should have done so many practice or assignment problems that doing it would be like second nature to you anyways. Of course, doing practice problems is the only way to get better at math. You can prefer not to attend any lectures and still ace a math course. Not that I'm recommending that method though; that depends on how you prefer to study.


I absolutely agree. Before I went in to the clinic and was diagnosed with Asperger's, one of the only doubts I had left as to the possibility of its nonexistence in my person was the often spoken-of property that Aspies tend to "accumulate a wealth of factual information about a subject, while sometimes missing the big picture" whereas I felt that this was absolutely not true about my interest in mathematics. I certainly enjoy the accumulation of "a bunch of facts" about mathematics, but due to the abstract nature of the subject, what is more interesting is precisely trying to understand the big picture, i.e. "the forest rather than the trees".

Being that you're the first mathematically inclined AS person who I've seen on here (I was just diagnosed yesterday), it helps to see that you do emphasize the big picture.

But regarding what you said, that describes my mathematical life perfectly.