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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.

    • 478 posts
  1. Started by Ondrej Janicko,

    Hi, I discovered reverse Fibonacci sequence. Can you comment me what you think and what math value have this discovery? The article is in attachment. Thanks. Reverse Fibonacci sequence Short - Ondrej Janicko.pdf

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    • 9 replies
    • 2.3k views
    • 1 follower
  2. Started by ennogs,

    I have been tearing my hair out over this lol. I am trying to work my holiday (vacation) entitlement out. Can somebody please tell me if I am right? I get 27 days holiday plus the bank holidays (public holidays). My work year is 1st of April to 31st of March. Due to Easter moving about that means this year I get 7 days as bank holidays. In total this year I get 34 days holiday entitlement If I worked full time I would do 7.5 hours per day and work 5 days per week = 37.5 hours per week. 34 holidays days x 7.5 hours a day = 255 hours holiday entitlement. If I was full time every time I take holiday day I would lose …

  3. Started by Z10,

    Hello, there are two circles in nature a real circle well defined in mathematics. And an imaginary circle in our head that can not be defined.

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    • 13 replies
    • 5.3k views
    • 1 follower
  4. Started by jfoldbar,

    i have a question for any maths wizz here. something from my real life. i have a toolbox with a padlock that opens via a 4-digit sequence. so, for example 8734. and the padlock opens. so when i lock the toolbox sometimes im a bit lazy and i just move the 4 slot around a bit, without touching the 873. one of the other guys reckons its easier for someone to work out the code to open the lock if i have only moved 1, instead of all 4 of them. is he right? or does the law of averages mean there are still the same chances someone will guess it regardless of how many or few i move.

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    • 4 replies
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  5. I am trying to find the maximum and minimum peaks of a function which goes as: y=x1 cos(f1+ teta) + x2 cos(2*f1); The peak values are straightforward for cases where the frequencies are equal or when they are non-multiples. I am having trouble to quantify the maximum and minimum values of 'y'. Note: teta, x1 and x2 all these vary from time to time. I am therefore looking for a generalised expression (accuracy <5%). Thanks in advance.

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    • 1 reply
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  6. So I was recently thinking about solar angles. A fairly straightforward, everyday example of solar angles. Or so you'd think. However, recently one thing came to mind. Suppose it was 6 hours before or after noon during a fall or spring equinox (for our purposes it wouldn't matter) at the equator. Since it was "halfway" between sun-over-the-horizon and sun-overhead, I presume the solar angle would be 45 degrees, right? Now suppose at the same time someone else was, let's say, at 45 degrees latitude; (north or south for our purposes wouldn't matter) at the same time. How would one determine, then, what the solar angle there would be? Is t…

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    • 5 replies
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  7. If the radius unit vector is giving us some direction in spherical coordinates, why do we need the angle vectors or vice versa?

  8. So I'm reviewing my rules of radicals prior to teaching it to students, and found out I'm a little rusty on them. Suppose you hit an answer that ends with a prime number as your radicand. Provided you used mathematically valid reasoning to get there, does this prime-number radicand now suggest that you arrived at the most simplified form, or are there "dead ends" distinct from the right answer?

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    • 2 replies
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  9. Discrete examples are easy enough. Toss a coin, 1/2, toss a die, 1/6. Continuous examples, Probability of a nucleus decaying during observation, 1-exp(-λt), Probability of a neutron moves x without interaction, exp(-Σx), where Σ can be assumed to be the inverse of the mean free path i.e. the distance a neutron travels without interaction on average. My point is that I don't really have an idea as to how these continuous probabilities are derived. Any assistance?

  10. Started by pechatnik,

    Probably the most accurate method of dividing any angle into three equal parts. Simple and accurate

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    • 3 replies
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  11. Started by Sidney johnson,

    For those who haven't used a rubix cube there are certain patterns you simply cannot achieve, for example if you flip exactly 1 corner to the right or left, either by taking it out or by simply twisting it you can not solve it without either twisting it back or twisting all other corners relative to it, or you can turn all but one other corner in different directions and then be able to solve it. Or you can turn all of the corners and try to solve it and you will only have one corner turned wrong. I can not figure out the math behind this. Can someone explain if you can.

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    • 0 replies
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  12. Started by Zolar V,

    Is anyone here interested in the Collatz Conjecture? If so I believe I have the solution, seriously, and I need to work with someone who knows how to write a formal proof better than I. There are some errors in my proof, but the underlying principle is right. I only have my minors in mathematics, so my proof writing skills are subpar.

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    • 128 replies
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  13. So I was recently thinking about the similarity in formulae between spheres' volume (4*pi*r*r*r/3) and their surface area. (4*pi*r*r) Firstly, I noticed that the surface area looks like it's the derivative of volume with respect to radius... which come to think of it makes sense as the rate of change in volume at a point in time is that outer spherical shell being added times its thickness. But secondly I also noticed that the ratio of the two is r/3. As in, as if the average particle in a sphere were only a 1/3 of the way to the outside. More generally, V/A is in length units. Am I figuring this right? Does V/A represent average distan…

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    • 2 replies
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  14. I discovered an improved method for finding large prime numbers by ignoring the prime numbers alltogether and only focus on the wavelike patterns of prime factors which is loosly related to the Sieve of Erasthonenes. Figure 1: The Sieve of Erasthonenes By noting that prime factors occur at regular intervals. ie multiples of 2 reoccur every other number, multiples of 3 reoccur at every third number, etc. we can leverage this periodicity of prime factors to identify all non-prime positions within a predifined large range of natural numbers arranged in an array. This periodicity of prime factors means that we can apply the concepts of Standing Wave Harmonics …

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    • 16 replies
    • 8.5k views
    • 2 followers
  15. Started by Rishit Patel,

    What is the use of Calculus in Computer Science?

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    • 3 replies
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  16. Started by Cristiano,

    I know the value of dn/dt (e.g. dn/dt = 123). a3 = 345 / n2 Is there any way to calculate da/dt?

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    • 9 replies
    • 2.1k views
    • 1 follower
  17. Started by studiot,

    This issue is offtopic in a thread about electrons so I have started a new thread for discussion. https://www.scienceforums.net/topic/115443-electrons-how-do-they-work/?tab=comments#comment-1062243 Finite is often used to mean a non-zero number https://en.wikipedia.org/wiki/Finite_number "In mathematical parlance, a value other than infinite or infinitesimal values and distinct from the value 0" I prefer the definitions of Dedekind : not infinite Russell : Able to be counted using a terminating sequence of natural numbers. Consider the equation x2 - 2x + 1= 0 Is the …

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    • 21 replies
    • 8.9k views
    • 2 followers
  18. Started by Brett Nortj,

    This statement is where we could use my own new type of maths I am trying to bring into secondary education through my company "Hydra." I have spent a lot of time planning new approached to maths, at secondary and tertiary levels, so, please bear with me and observe where the strengths are of my new system? This is just an example of how it can be applied, of course. [9H] * [6K] * [2X] * [1Q] = [108A]. This is because the powers can be applied to the symbols and then taken as '[X1]'. This leads to a simple set of symbols to multiply. Then, we take the [108A] divided into the symbols on the left that we recognize, being [H], [X] and [K], coming to [HXK] = [108]. …

  19. Started by Brett Nortj,

    This would be [infinity] * [2n] = [3] * [2] = [6] * [x] Then, [5] * [2] = [10] * [x] Then, [7] * [2] = [14] * [x] So, the answer is double prime times by [x]. Or, [N] * [2] *[X].

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    • 19 replies
    • 2.7k views
    • 2 followers
  20. Started by ALine,

    Is there an easy straightforward way to produce a mathematical model for anything that I can imagine? The more that I think about it the more and more that I see that maybe everything could be written as a function with distinct variables. I just want to know how I can make mathematics seem extremely intuitive so that if I see a leaf fall on the ground I could fully model that falling in all case scenarios with either a simple algebra equation or with a more complex differential and multi-variable calculus equation. I have had the urge for years so if anyone could help that would be great.

  21. Started by geordief,

    What is (unless there is more than one definition,perhaps?) the mathematical definition of a surface in a general sense? I am interested to know in the context of intrinsic curvature but feel I need to get this concept well understood first. For example must a mathematical "surface" in a 4-D space be 2-dimensional (like a skin) or is it 3-dimensional (like a volume)? If it is 3-dimensional,what defines it as a surface?

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    • 16 replies
    • 7k views
    • 1 follower
  22. Every second, a green marble has a chance to appear. You are not told what the probability of this occurring is - instead, you are given a number which is equal to the average number of seconds it takes for a green marble to appear (let's call it 'mean time to happen'). Now let's say you want there to be a chance of a red marble appearing instead of a green one. In order to make this happen, you must define a separate 'mean time to happen' for the red marbles. But you do not want to change the overall chance of any marble to appear; the combined probability of a red or green marble appearing must be the same as the previous probability of a green one appearing. …

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    • 3 replies
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  23. Started by Cristiano,

    I know that the area of an ellipse is 1403761773.43497 and its circumference is 145485.418131498. Is there any way to calculate from those numbers that the semi-major axis is 26534.9039306654?

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    • 4 replies
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  24. Started by barryalen1992,

    I started to study about diff eq for this summer class. And I already have trouble with it. The professor lecture is also probably too fast and I couldn't get anything to my brain. Is there any site exclusively for this matter? Please tell me.

  25. Started by Dr Finlay,

    Me and a few friends at school the other day were wondering if pi and phi were somehow connected, After a while i managed to throw out [math]\phi^{(\displaystyle\frac{\pi + \phi}{2})}= \pi[/math] which manages to roughly approximate [math]\pi[/math]. I then found if you did [math]\phi^{(\displaystyle\frac{\pi + \phi}{x})}= \pi[/math] with [math]x = 2.000811416[/math], the equation exactly reached [math]\pi[/math]. But [math]x = 2.000811416[/math] seems too random to me, is there any connection between [math]\pi and \phi[/math] that would produce [math]x = 2.000811416[/math]? On the slight chance you understood what i said, do you know where [math]x = …

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    • 16 replies
    • 20.3k views
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