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Mathematics

From algebra to calculus, from trigonometry to set theory, it's all here.

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  1. From basic sequences, series and calculus, to measure theory, complex analysis and more advanced topics.

    • 1.2k posts
  2. Set theory, groups and ring theory, linear algebra, and other algebra-related topics.

    • 538 posts
  1. Started by Shadow,

    Hey all, Where am I making a mistake? [math]-i=(-1)\sqrt{-1}=\sqrt{(-1)(-1)(-1)}=\sqrt{-1}=i[/math] Cheers, Gabe

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    • 11 replies
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  2. If it takes 1 calorie to raise the temperature of water by 1 degree Celcius, will it take 100 calories to bring the same amount of ice to a boil?

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    • 4 replies
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  3. Started by johan01,

    Are there certian postulated math axioms, that cannot be proven. Do these axioms ( if they exist) , constitute the basis of all mathematics. If so where can i get more info?

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    • 13 replies
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  4. This is a question about the nature of Mathematics as a language. The question is very simple, as the thread name suggests, but I’ll expand my own perception of it here and so it would be helpful if someone can leave a few comments. Is mathematics relative or absolute? My insight developed as follows…; If Mathematics as language was invented by us it was definitely invented based on the observations of the physical space and laws on our planet. To simplify; we can find one thing in common between 2 yellow stones on one location and then 2 blue stones on another – the fact that there are 2 stones in each group. So number 2 is the commonality. If we add these 2 groups …

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    • 18 replies
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  5. Started by carl1,

    the maximum kinetic energy of a photoelectron, Ek,max , to the smallest amount of energy, E0, needed to free an electron from the metal, and the energy, Eph , of the incident photons of light: Ek,max = Eph – E0 In addition, you know that Eph = hf where h is the Planck constant and f is the frequency of the incident light. Which one of the following graphs represents the relationship between Ek,max and f ? please help answer due tomorrow. Carl1.

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    • 1 reply
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  6. Started by bob000555,

    What is i to the power of infinity? As near as I can figure either the answer is the matrix [-1, 1, i , -i], or 0.

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    • 5 replies
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  7. Started by ajb,

    Does anyone know a good book, review article etc. on differential graded Lie algebras? I need to know some basic results/theorems from dg Lie algebras as I have what I think is a generalisation. Thanks.

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  8. Started by Petanquell,

    I'm not sure, if it is a senceful question but... I always get angry when someone write something like [math] \lim_{x \rightarrow 2 }\left(\frac{x^2-4}{x-2} \right) =4 [/math] because it's not equal ,it approximates, it's "almost equal". I know, it's mathematicly correct, but something's telling me that the equality is not the best symbol for this. The question is if the "4" on the right represents number or constant function (and my opinion is it should end in this [math] \lim_{x \rightarrow 2 }\left(\frac{x^2-4}{x-2} \right) =\lim_{x \rightarrow 2 } (4) [/math] formula without other editing, if it is a function...) and if that "4" is a real number, why is there e…

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    • 9 replies
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  9. Started by Gareth56,

    Could some kind soul explain the simplification of the following sin(theta) + mucos(theta) = cos(theta) - musin(theta) tan(theta) + mu 1 - mutan(theta) I understand that sin(theta)/cos(theta) = tan(theta), but cannot work out how the 1 - the rest comes from. Thanks

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    • 6 replies
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  10. Started by carl1,

    Hi all, how would you find the kinetic energy of a sparrow of 28.6 g moving at a speed of 13 M S^-^1. Thanx.

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    • 6 replies
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  11. Started by ajmeri,

    Which of these relation on the set of all people are equivalence relation ? Determine the properties of an equivalence relation that the other lack. (1) {(a,b) | a and b are the same age} (2) {(a,b) | a and b have the same parents} (3) {(a,b) | a and b share a common parents} (4) {(a,b) | a and b have met} (5) {(a,b) | a and b speak common language} Appreciate your reply.

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  12. I dare anybody to try and disprove the fact that 0.9999999..... repeating doesn't equal 1. In particular, read some of the proofs on this website here: http://www.qntm.org/?pointnine Good luck

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    • 3 replies
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  13. While thinking about random walk on a graph, standard approach is that every possible edge is equally probable - kind of maximizing local entropy. There is new approach (MERW) - which maximizes global entropy (of paths) - for each two vertexes, each path of given length is equally probable. For a regular graph it gives the same, but usually they are different - it MERW we get some localizations, not known in standard random walk. It was derived in http://www.arxiv.org/abs/0710.3861 in the context of optimal encoding. In http://www.arxiv.org/abs/0810.4113 are analyzed it's localization properties. It can also suggest the nature of quantum physics ( http://www.advanc…

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  14. I made a thread with general exploration of the concept of portals before but now I want to just explore this scenario. I was wondering where to put this but I think that it needs to be explored mathematically to be solved although I would be grateful if explanation would be given as well as mathematics. For this thread what I will be calling portals are 2D areas of space in a 3D environment, they behave physically like an other very thin thing would. They can't bend and are rectangular. They are one sided and the back side is solid, things cannot pass though the solid parts. There are thin edges around the front side much like the frame of a picture, they are also so…

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    • 2 replies
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  15. Started by Shadow,

    Hey all, just a quick question, does anybody recognize a pattern in the following numbers...? 1, 2, 2, 3, 4, 3, 5, 4, 6, 7, 5, 3... I can post more if you need them. Cheers, Gabe

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    • 1 reply
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  16. Started by meatbag,

    I know this is a stupid question but Im going to ask it anyway Ive written an iterative algorithm in C (programming language) and wondered how to represent this in maths. For example, int main(void) { int x; for(x=40; x>0; x/=2) { process(x); } return 0; } So each of the following is put into the equation... 40 20 10 5 2 1 Basically all I want to know is what do you use in maths to represent equating a formula with a range of input values?

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    • 17 replies
    • 2.7k views
  17. Started by komrane,

    Hi everyone, I want to find a function to fit a two arrays data (X,Y=f(X)) with high precision, but I am not succeed. Can any one help me. These are my data: X={1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19 ,20,21,22,23,24,25,26,27,28,29,30,31,32, 33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49 ,50,51,52,53,54,55,56,57,58,59,60,61, 62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78 ,79,80,81,82,83,84,85,86,87,88,89,90, 91,92,93,94,95,96,97,98,99,100,101,102,103}; Y={-3.82047923,-4.78741509,-3.7235349,-3.83978508,-4.05577459,-4.30089612,-4.533835, -4.74829898,-4.94488133,-5.12552735,-4.85195336,-4.7612524,-4.68355948,-4.69161082, -4.73528276,-4.79596239,-4.…

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    • 3 replies
    • 1.5k views
  18. Started by Shadow,

    Hey all, While this is a sort of computer oriented problem, I decided to put it in General Mathematics, because the answer to this question will be a math answer. So on we go. When you tell the computer to draw a circle with a diameter x on the screen, it won't draw a perfect circle. Why? Well, let's skip the "Pi is irrational part" for a second. The screen is made of pixels. Pixels are squares. So, ultimately, the shape we see is lots of tiny squares put together so as to form something resembling a circle. But it's not a circle. It's squares. Now here's what I need; how does a computer know, based on the diameter of the circle that we want it to draw, how many s…

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    • 4 replies
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  19. Started by HannonRJ,

    Does an equation that describes a physical situation apply to a situation in which one of its parameters does not exist?

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    • 2 replies
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  20. Started by streak,

    there is a triangle ABC.Find the locus of point X such that area of triangle ABX=area of triangle XAC.

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    • 0 replies
    • 801 views
  21. Started by Shadow,

    Hey all, I was thinking the other day, I know it's possible to have, say, base [math]\pi[/math] number systems...but what about base one? Or base smaller-than-one, eg. [math]1/2[/math]? Or negative bases? Or fractional bases? How would one convert to and from those systems? Cheers, Gabe

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    • 5 replies
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  22. Started by ggyyree,

    I have got a quadratic form as following: F(w) = g^T * w + (1/2)* w^T * B * w Here T is the matrix transpose. Someone said the if p is a solution to this quadratic form then p is a solution to an equation of the form: (B + aI) * p = -g Here I is the identity matrix. May I ask why please? Thanks a lot!

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    • 0 replies
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  23. Started by carl1,

    hi all, can anyone please help. Im stuck on calculating the volume - If you had a mass of 1.028 x 10^26 kg and density of 1.61 x 10^3 kg m-3. I have come up with what i think is the answer that is 0.63850931677m^3 If this is correct, then how do i write this answer to the appropriate number of significant figures. Many thanks Carl1

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    • 1 reply
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  24. Started by oranphil,

    Is it true what people say to me that maths s easy and all it is a logical puzzle because i am so bad at it?

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    • 8 replies
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  25. Started by NIN,

    Hi, does anyone have an "order" of maths? I know it sounds strange, but I need a list of different types of maths, and in which order they should be explored. I hope to be a mathematician or a physicist someday, but I'm still struggling with the 10th grade math that I'm doing now >.< so I'd like some type of list, so that I can first perfect the current math that I'm doing with online guides, then know where to move next. Also, this would help me ace a lot of my math tests. If anyone has any advice, or a link or anything of the sort, it'd be greatly appreciated. Thanks.

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    • 3 replies
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