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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
  3. Home to threads on more applied (but non-physical/mechanical) threads; e.g. applied group theory or statisics.

    • 464 posts
  1. Started by square173205,

    Is 1+1 always 2? I tried to prove that 1+1 is not always 2 with applying Goedel's incompleteness theorem as; http://hecoaustralia.fortunecity.com/incompleteness/incomplete.htm

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    • 7 replies
    • 1.7k views
  2. Started by Saber,

    Is the only reason that our mathematics are 10 based because we he 10 fingers and the first calculator was only our fingers ?

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    • 11 replies
    • 1.9k views
    • 1 follower
  3. Started by Penumbra,

    Hi, I am 100% new to all of these boards. I have been drawn here because I saw a science forum, and inside of that an astronomy and cosmology forum (!). I thought it would be better to ask here, and not in science for my question about scientific notation. I remember learning about this, a long time ago, but I have forgotten, and need help. =\ Is there any easy way (minus using a calculator) to solve equations such as 26^78 or 13^90 and so on? I'm just making up these numbers at random, so please be gentle. I appreciate any help!

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    • 11 replies
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  4. Consider this riddle. The result it claims is fairly remarkable, and yet the solution, although a bit difficult to digest at first, is logically sound, but based on axiom of choice. Just sharing it because I think it is really cool, and I figure this community would enjoy.

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    • 2 replies
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  5. Started by Ramsey2879,

    Actually my problem is to find my proof that there are an infinite number of solutions to the Diophantine equation 5a^2 + 5ab + b^2 = p^n where a,b are coprime and p is a prime ending in 1 or 9. There is a relationship between any three consecutive term of a Fibonacci type series and the form 5a^2 + 5ab + b^2 that is invariant with the index number of the first term. That is a key to my proof. I leave the proof for you to figure out, but will make suggestions if you reach a dead end and have no idea where to turn. First off then, how does the form 5a^2 + 5ab + b^2 relate to three terms of a Fibonacci type series in an invariant manner? (By Fibonacci type, I mean F(n…

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    • 1 reply
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  6. Started by Martinez,

    In the process of a patent/copyright research I happened upon a copyrighted 12-tone Scientific Scale. Don't know what the application of it might be, bu do know that the 7-tone Scientific Scale of Pythagoras is the standstill to mathematics in the Western world. In any event I copied it down to give here should there be the interest: 12-tone Scientific Scale: F#= 1.4046639.... C= 2.0 (fundamental) C#= 1.0534979.... G= 1.5 G#= 1.5802469.... D= 1.125 D#= 1.1851851.... A= 1.6875 A#= 1.7777777.... E= 1.265625 F = 1.3333333.... B= 1.8984375 Do not confuse the scale with ton…

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    • 0 replies
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  7. Started by EratosthenesII,

    Perfect squares end in 1,4,5,6,9 and zero. Nice symmetry. Especially with the squares of 1 & 9 (5 +/- 4) ending in 1 2 & 8 (5 +/- 3) ending in 4 5 (5 +/- 0) ending in 5 4 & 6 (5 +/- 1) ending in 6 3 & 7 (5 +/- 2) ending in 9 WHAT ABOUT SQUARE ENDINGS? 100, 400, 900, 1600; of course, if a number ends with a zero, its square ends in 00 Is the only other repeated end for a square 44? 144 1444 3844 7744 12544 19044 26244 35344 44944 56644 68644 are all perfect squares their square roots are (50n +/-12)2 and n = 0,1,2 . . . For further amusement, 213,444 = 4622, and is the second member …

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    • 1 reply
    • 1.3k views
    • 1 follower
  8. Started by Daecon,

    I was reading about the Arecibo message thingy, with the message being transmitted in 1679 bits because there's only two ways to lay out 1679 in a grid, one of which would make "sense" and one that wouldn't. Then I thought, this would only work if aliens used a square grid system (where information can have x & y co-ordinates) for their layouts, which there's no guarantee they would... What if alien visual representations or data were laid out on a hex grid? Maybe they would arrange them from the center spiraling outwards either clockwise or counter-clockwise. Maybe they would be arranged in rows and zigzag columns, or columns and zigzag rows, or maybe …

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    • 0 replies
    • 854 views
  9. Started by kingjewel1,

    When does 1 and 1 make 3? Happy New Year

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    • 13 replies
    • 4.1k views
  10. Started by gib65,

    Does anybody else find this fascinating--that if both operands are 2 for any "growth" operator, then the result will always be 4. By a "growth" operator, I mean +, x, power, etc.--and operation whose result is greater than its operands (as opposed to "shrinking" operators like -, /, square root, etc.). 2 + 2 = 4 2 x 2 = 4 2 ^ 2 = 4 2 # 2 = 4 (where we could suppose x # y means x raised to itself y times). Wouldn't this trend go on indefinitely? Couldn't we say that 2 @ 2 = 4 where @ is any "growth" operator whatever? And wouldn't a similar rule apply where 4 % 2 = 2 where % is any "shrinking" operator whatever? NOTE: I'm aware that I've defined "growth"…

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    • 5 replies
    • 2.4k views
  11. Started by Caleb,

    Here is a strange equation I found: a=b a^2 = ab a^2 - b^2 = ab - b^2 (a + b)(a - b) = b(a - b) a + b = b (a = b) a + a = a 2a = a 2 = 1 This still works, even if you substitute "a" and "b". 2 = 2 2^2 = 2(2) 2^2 - 2^2 = 2(2) - 2^2 (2 + 2)(2 - 2) = 2(2 - 2) 2 + 2 = 2 4 = 2

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    • 11 replies
    • 2.2k views
  12. Hello everyone I have 2 questions: First of all, I'd like to know if these (notations) are correct: [math]\left(u_n=\sum_{i=0}^{+\infty}{10^i}\right)\equiv (1,0,1,0,1,0,\cdots )\bmod11[/math] [math]\left(u_n=\sum_{i=0}^{+\infty}{10^i}\right)^2\equiv (1,0,1,0,1,0,\cdots )\bmod11[/math] Secondly and finally, I'd like to know if it's possible to prove that the row [math]\left(u_n=\sum_{i=0}^{+\infty}{10^i}\right)=(1,11,111,1111,11111,111111,\cdots)[/math] has no prime numbers in it (11 excluded)? Thank you! -Function P.S. Could the title please be changed to "2 characteristics of the row (1, 11, 111, 1 111, ...)"? Thanks.

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    • 2 replies
    • 1.3k views
    • 1 follower
  13. Started by devrimci_kürt,

    Why 2 multiply 2 is equal 4?proof?

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    • 3 replies
    • 1.4k views
  14. Started by Externet,

    Two identical ships next to each other in the middle of a river heading against the current; one at full throttle developing 1000 horsepower just counteracts the current and does not advance at all. The other is anchored. How many horsepower does the anchor produce ?

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    • 49 replies
    • 6.7k views
  15. Started by Bek,

    Hello, everyone! Can you explain me what can we measure in 4 dimensional space? If, in 2d - Area, 3d - volume.... Thank you!

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    • 5 replies
    • 7.1k views
  16. Started by md2,

    suggestion : 2r is diagonal of square inside the oval

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    • 3 replies
    • 1.2k views
  17. Started by ted,

    Greetings: I am a first time user of this web site, so, Imay make a few mistakes. I want to re-learn the formula for determining the diagonal distance between the ends of a 3-4-5 right triangle. The the known measurements are 10 ft and 12 ft.

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    • 8 replies
    • 2.5k views
  18. It is probably a too long of title, but this question loomed in my mind. We all know that 3 dimensional geometric volumes have a finite size(unless told otherwise), and 2 dimensional shapes are made up of lines that are infinitely thin. However, 3 dimensional volumes such as cylinders are made up(theoretically) of 2 dimensional circles that are stacked upon each other until a given height, yet 2 dimensional shapes with lines that are infinitely thin are able to make up a certain height. How is this possible? I mean the formulas for determining surface area and volume are based on these principles, though I could be wrong.

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    • 4 replies
    • 1.5k views
    • 1 follower
  19. Its the last round of a game show. You have to choose between three doors labeled One, Two, and Three. Behind each door is a prize. Now two of the doors contain goats while one of the doors contains a brand new car. Your asked to choose a door number. Lets say you choose 1. The Host then reveals a door other than the one that you choose, lets say that it is door number 3, and it has a goat behind it. You are then asked if you would like to change your choice to number 2 or stick with number 1. Now the riddle is, does this make a difference? Should you change your answer or stick with it? Have you all heard of this wierd puzzle? I have a book about it, but t…

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    • 86 replies
    • 14.8k views
  20. Started by mScientist,

    Hi, I have two points in 3D space: point A: (1,2,3) point B: (4,7,6) I want to find a third point between the two, where z = 5 So, point C: (x,y,5) How can I calculate x and y for point C. Thanks.

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    • 3 replies
    • 2.3k views
  21. Started by fiveworlds,

    Trying to setup 3D Math right in svg here's how far I have gotten. The Z axis is obviously a translation on the x and y co-ordinates. At the moment I am using a translation of 1 but I am wondering would it be right to use the square root of 0.5? <script> function Three_Dimensional_Resolve_Points(matrix){ var svg = {width:800, height: 800}, midpoint = {x:svg.width/2, y:svg.height/2}; Z_Translate = {X : -1, Y : 1} X = matrix[0] + (matrix[2]*Z_Translate.X) + midpoint.x; Y = matrix[1] + (matrix[2]*Z_Translate.Y) + midpoint.y; return [X,Y]; } svg = { width : 800, …

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    • 3 replies
    • 1.5k views
  22. Started by AgentBurn,

    I need a formula to calculate all three coordinates a third point of a triangle. Here is a sketch of a random triangle just so it makes it easyers for me to explain my problem: TRIANGLE I have x,y and z of points A and B, and lenght all of the sides (a,b and c) The third point, C, must be between A and B in x-z axises (that should reduce the solutions from a circle (actualy the edge of a circle, i dont know the english term) to only 2 points), and I only need the point that is above the line c on y axis. I could calculate that manualy, but i need a formula that works allways becouse i need it for the movement of my robot (it isnt homework, just a project =…

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    • 0 replies
    • 1.2k views
  23. Started by Krz,

    a friend of mine said there was a way to prove 4 is more than 5 could anyone please explain?

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    • 14 replies
    • 2.4k views
  24. Started by mrgriffxy,

    So there is this weird phenomenon that occurs when you follow these specific rules: If ODD 3x+1 If EVEN x/2 The theory is that if you take a number through these rules as far as possible you will achieve a never ending cycle of 4,2,1. So say for instance you start with 5 follow the ODD function to get 16 then even function for 8 again for 4 again for 2 again for 1 then 4, 2, 1, 4, 2, 1... As far as I am aware this has not been proven to work for every number and it is unsure if there could be other sequences like this that appear from numbers untried. I guess my point is for a discussion to see if it can't be proven.

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    • 20 replies
    • 5.5k views
    • 1 follower
  25. This is the problems on the 46th International Mathematical Olympiad. My friends got excellent result from it, some of them are still very young, the youngest is 2 years smaller than me. That could depress me much. [as I even could not get the qualification to join the competition] http://gifted.hkedcity.net/Gifted/ActReview/imo2005Mexico/pdf/1dayenglish.pdf http://gifted.hkedcity.net/Gifted/ActReview/imo2005Mexico/pdf/2dayenglish.pdf

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    • 5 replies
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