Numbers Definition and 1000 Threads

  1. D

    Arbitrary array of numbers, proof

    Homework Statement The numbers 1 to 25 are arranged in a square array of five rows and five columns in an arbitrary way. The greatest number in each row is determined, and then the least number of these five is taken; call that number s. Next, the least number in each column is determined, and...
  2. phion

    Colored Words or Numbers in VB6

    Hi, I've written some code in VB6, and I'm trying to figure out how to add color to individual words and numbers. The program is a console application Roulette game. What I need to figure out is how to make my money green if positive and red if negative, and color the words "red" and "black"...
  3. L

    Complex numbers - I'm sure this is an easy - Argand diagram

    Homework Statement OABC is a square on an Argand diagram. O Represents 0, A represents -4 + 2i, B Represents z, C represents w and D is the point where the diagonals of the square meet. (There are two possible squares that meet this criteria) Find the complex number represented by C and D in...
  4. S

    MHB Complex numbers and conjugates

    Hi everyone, Can you please assist with the following problem? The complex numbers z and w are such that for the real variable x, (x-z)(x-w)=ax2+bx+c for real a,b and c. By letting z=p+qi and w=r+si, prove that z and w must be conjugates of one another.So far, I have determined that a=1...
  5. J

    Proving that the natural numbers are countable, stuck.

    Homework Statement [/B] I'm working through a problem in Abott's Understanding Analysis, second edition, the statement of the problem being: "Fix a member n of the natural numbers and let An be the algebraic numbers obtained as roots of polynomials with integer coefficients that have degree n...
  6. N

    Why my synchronous counter toggling between two numbers?

    EDIT: SOLVED I designed a bi-directional synchronous counter with the sequence 7 4 6 5 2 1. The up count counts correctly (ie 7 4 6 5 2 1) but when I flick the switch to reverse it it counts backwards correctly initially until it reaches 5, and then it goes back to 2 and then back to 5 and...
  7. R

    Engineering Combinational circuit that multiplies two numbers together

    Homework Statement Design a combinational circuit that multiplies two numbers together, and outputs the result. Homework Equations The biggest product will be 3 * 3 = 9. Four bits to represent the product. 0: 00 1: 01 2: 10 3: 11 I need a 4 bit register for the outputs The Attempt at a...
  8. Gjmdp

    Why Nitrogen has 5 Oxidation Numbers that are false?

    My Chemistry Teacher told that 5 of the 6 oxidation numbers of Nitrogen are not true. He said something like it is a mathematical trick for I don't know what. The real oxidation number is -3. Can anyone explain me what are the 5 false oxidation number? Thank you.
  9. micromass

    Insights Informal Introduction to Cardinal Numbers - Comments

    micromass submitted a new PF Insights post Informal Introduction to Cardinal Numbers Continue reading the Original PF Insights Post.
  10. R

    How to Write Canceled Numbers in Word 2010?

    Hello, I want to know how to write the canceled numbers in a fraction using Microsoft Word 2010. Please see the attached image. Thank you.
  11. K

    Are there prime numbers n for which S=/0?

    We have the set:S={1<a<n:gcd(a,n)=1,a^(n-1)=/1(modn)} Are there prime numbers n for which S=/0?After this, are there any composite numbers n for which S=0? (with =/ i mean the 'not equal' and '0' is the empty set) for the first one i know that there are no n prime numbers suh that S to be not...
  12. C

    Dealing with very large and very small numbers

    Are the following correct (all numbers are approximations); d from the Earth to the Sun is 90 million miles = 9 x 10^ 7 miles = 144 million km = 1.44 x 10 ^ 8 km ? d from the Earth to the Moon is 240 thousand miles = 2.4 x 10^ 5 miles = 400 thousand km = 4 x 10 ^ 5 km? m of the Earth = 6 x...
  13. Raffaele

    Square numbers between n and 2n -- Check my proof please

    I noticed that for any integer greater than 4 there exists at least one perfect square in the open interval (n, 2n). I think I have proved the statement, but as I am not a professional, I'd like someone to review my proof. By induction we see that it is true for n=5 because 5<9<10. Now suppose...
  14. S

    Exploring Imaginary Numbers for Beginners

    What are imaginary numbers? Does anyone know a good book for it?
  15. B

    Complex numbers and beyond....

    If the solution of the quadratic equation \frac{-b \pm \sqrt{b^2-4ac}}{2a} produces a new kind of number, the complex numbers a \pm i b so, the solution the cubic equation should to produce a new kind of number too, and the solution of the quartic equation too, etc...
  16. Albert1

    MHB Max n for Sum of 3 Numbers Multiple of 27 in A

    $A=\begin{Bmatrix} {1,2,3,4,5,------,2015} \end{Bmatrix}$ if we pick $n$ numbers from $A$, we call it the set $B$ ,and the sum of any three numbers from $B$ are multiple of 27 ,find $max(n)$ , and the largest number we can choose from $A$
  17. A

    Complex numbers and negative roots

    I was wondering if scientists or mathematicians have any use for complex numbers involving negative roots of I as in i=(-1)^(1/2). but my question is more what would be (-1)^(-1/2)?
  18. anemone

    MHB Find al the four-digit numbers ABCD

    Find all the four-digit numbers $ABCD$ which when multiplied by $4$ give a product equal to the number with the digits reversed, $DCBA$. (The digits do not need to be different.)
  19. P

    MHB Prime Versus Irreducible Numbers

    I don't quite know where to start with this one: "A natural number p>1 is called irreducible if it has the property that, for any natural numbers a and b, p|ab always implies that either p|a or p|b (or both). Prove that if a natural number p>1 is irreducible, then it also has the property...
  20. H

    Please help me prove this statement about square numbers

    Hi, a friend of mine gave me a math problem which I've spent hours trying to find different methods to solve. But none of them work and I'm now out of ideas. The problem goes like this: So for example, ##17^2 = 1^2 + 2(12^2) ⇒ 17 = 3^2 + 2(2^2) ## or ## 3^2 = 1^2 + 2(2^2) ⇒ 3 = 1^2 + 2(1^2)##...
  21. RJLiberator

    Show that Odd Euler Numbers are 0

    Homework Statement Complex Analysis Problem: The euler Numbers E_n, n=0, 1, 2,..., are defined by 1/cosh(z) = the sum from n=0 to n=infinity of E_n/n! z^n (|z|<pi/2). show that E_n=0 for n odd. Calculus E_0, E_2, E_4, E_6 Homework Equations Not entirely sure what to put here for this one...
  22. M

    Roots of Negative Numbers (Complex Analysis)

    Homework Statement Express (-1)1/10 in exponential form (My first time posting - I hope I got the syntax right!) Homework Equations The Attempt at a Solution [/B] I got the solution, it's ejπ/10, but I'm not sure why. Here's my work: (-1)1/10 = (cos(π) + jsin(π))1/10 = cos(pi/10) +...
  23. S

    Understanding // in the Hint for Showing Numbers of Form ±m√2/n Are Dense

    Hello, Please, someone, explain what the // in the hint below stands for: "Show that the numbers of the form ±m√2/n for m, n ∈ N are dense." Hint: "To find a number in (x, y), find a rational in (x//√2, y//√2). Conclude from this that the set of all (irrational) numbers of the form ±m√2/n is...
  24. Curieuse

    Rational and irrational numbers

    Homework Statement Determine a positive rational number whose square differs from 7 by less than 0.000001 (10^(-6)) Homework Equations - The Attempt at a Solution Let p/q be the required rational number. So, 7> (p/q)^(2) > 7-(0.000001) ⇒ √(7) > p/q > √(7-.000001) ⇒√(7) q> p >...
  25. Albert1

    MHB The numbers of non-primes in S

    $S=({10^1+1,10^2+1,---------,10^{1000}+1})$ please prove the non-prime numbers in $S \geq 990$
  26. Carlos Gouveia

    Exploring the Physics of Acceleration

    A car goes from repose (0 mph) to 50 mph in, say, 30 seconds. Math tells us that there is an infinite amount of numbers between 0 and 50 (or between any two other numbers). Therefore, isn't it "obvious" or "intuitive" that it would take a car an infinite amount of time to go from 0 mph to 50...
  27. A

    Why Does Setting m=0 Matter in Calculating Complex Numbers?

    Hi,I'm facing a problem finding the values of complex numbers, I'll put two examples then I'll explain the issue. ex1: (-e)^{iπ} , my answer is (-e)^{π^2±2mπ^2} The book answer is (-e)^{π^2} ex2: e^{2 arctanh(i)} , my answer is e^{[iπ/2±mπ/2]} = ie^{±mπ/2} The book answer is i...
  28. P

    Standard representation for arbitrary size/precision numbers

    Is there a standard way of representing numbers of arbitrary size or precision for storage in a text file, JSON message, variable etc.? I am thinking of representing integers as decimal strings e.g. "-12345678901234567" and floats as an ordered pair (array) of strings representing decimal...
  29. K

    MHB Proving Prime Numbers in Quadratic Imaginary Fields

    Hi, I need your help with the next two problems: 1) If p is a prime number such that p\equiv{3}\;mod\;4, prove that \sqrt{-p} is prime in \mathbb{Z}[\sqrt[ ]{-p}] and in \mathbb{Z}[\displaystyle\frac{1+\sqrt[ ]{-p}}{2}] too. 2) 2) We have d > 1 a square-free integer. Consider the quadratic...
  30. C

    MHB Finding Mean of a Set of Abstract Numbers

    Hello, I'm having a little trouble figuring out the following problem: Consider the set of number a, 2a, 3a, ..., na where a and n are positive integers. (i) Show that the expression for the mean of this set is \frac{a(n+1)}{2}. So far the only work I've been able to muster up is: Mean =...
  31. J

    Finding Complex Numbers: Solving Re(z) = 4Im(z)

    Find three different complex numbers that satisfy the equation in the form a + bi. I know that: Re(z) = a + bi = a Im(z) = a + bi = b Re(z) = 4Im(z) a = 4b I'm stuck after this point. How do you find what is a and what is b?
  32. U

    What are the quantum numbers (n, L, J)?

    Homework Statement [/B] I'm supposed to find the quantum numbers (n, L, J) for the first 3 energy levels in Iridium (Z=77), given that the first 4 ionization energies are ##76.1, 13.4, 12.8, 11.2 keV##. Homework EquationsThe Attempt at a Solution I know that the electronic configuration is...
  33. S

    MHB Adding numbers with exponents (confusion)

    Alright here's my confusion, if i take say 3x^2 + 4x^2 ill end up with 7x^2 which i accepted was the correct way to think about it, but if i try the same problem without the x variable doing the same method, 3^2 + 4^2 = 7^2 this is obviously not the correct answer. Instead 3^2 = 9 and 4^2 = 16...
  34. G

    Are There Infinitely Many Prime Numbers Written as ak+b?

    Homework Statement Prove that there are infinitely many prime numbers written ##ak+b##, with ##a,b,k## integers greater than 1 Homework EquationsThe Attempt at a Solution Please could you tell me if you agree with that proof ? By contradiction: Assume that there is an integer ##k## such that...
  35. anemone

    MHB Solving for x: Four Positive Real Numbers

    Let $a,\,b,\,c,\,d$ be different positive real numbers such that $a+\dfrac{1}{b}=b+\dfrac{1}{c}=c+\dfrac{1}{d}=d+\dfrac{1}{a}=x$. Find $x$.
  36. anemone

    MHB Proving $m+n=xy$ Using Positive Real Numbers

    Let $x,\,y,\,m,\,n$ be positive real numbers such that $m^2-m+1=x^2$, $n^2+n+1=y^2$ and $(2m-1)(2n+1)=2xy+3$. Prove that $m+n=xy$.
  37. W

    Figuring out kyle numbers for matrices/

    Homework Statement http://www.math.harvard.edu/archive/21b_spring_09/faq.html I'm having trouble understanding this explanation, particularly this part. "The Kyle numbers are 1, 2 because adding the first to 2 times the second column gives zero. " Sorry for this basic question but I was...
  38. Stoney Pete

    How to construct the natural numbers with hypersets

    I'm not a logician or mathematician but a philosopher (with dyscalculia) so please forgive me for skipping the technicalities... My question is this: Is there in the theory of non-well-founded sets (hypersets) something analogous to the set-theoretic construction of the natural numbers in ZF...
  39. evinda

    MHB Is $\Theta(m^2)$ the best time complexity we can achieve for this problem?

    Hello! (Wave) There are given three vectors $V_1, V_2, V_3$ of dimension $m$, the elements of which are real numbers. I want to write an algorithm that determines if there are three numbers, one of each of the matrices $V_1, V_2$ and $V_3$, that have sum equal to $0$. Can you write an...
  40. R

    Determining electron configuration with quantum numbers n l

    This relates to a question I asked recently on Quantum Dots, but I'll rephrase it and hopefully any chemists out there can help. If we have (n,l) = (1,2) where n and l are quantum numbers can we determine the orbitals? and hence the number of electrons in a quantum dot? i.e. And also I've...
  41. ChrisVer

    C/C++ Generating Random Numbers in C++ for Scientific Applications

    Hi. I am trying to create a program that I will give the maximum range (1,...,max) from which to generate random numbers, and make it generate N=maxgen random numbers (which later I can use for example in another program). Below you can see the code I wrote: #include <iostream> #include <ctime>...
  42. I

    MHB How Does Probability Change as I Draw Numbers from a Barrel?

    Hi I am not even sure if probability can answer this question but I hope it can. I have 400 numbers which I draw from a barrel one at a time. I am uncertain as to weather or not all 400 are in the barrel ( they might have been stolen) but I am unable to check. I am trying to calculate the...
  43. nomadreid

    Recursive sets and recursive numbers: relationship?

    Given the two standard definitions (1) A computable set is a set for which there is an algorithm which terminates after a finite amount of time and correctly decides whether or not a given number belongs to the set. (2) A computable number is a number which can be approximated to any degree of...
  44. Dethrone

    MHB Determinant - Proof for distinct real numbers

    I was able to prove a), but I am unsure how to prove b. Is there some sort of geometric interpretation I should be aware of?
  45. B

    Finding the centroid of a triangle using complex numbers

    Hi all, I'm preparing for a deferred exam this semester after falling ill last year. Just looking over my course notes and have a question. I understand how this works in the big picture scheme. What I don't understand however is how my instructor simplified the original equation. 1. Homework...
  46. X

    Circuit analysis complex numbers

    Homework Statement I'm going crazy. I've done this problem nearly 20 times and keep getting the same answer. I've read my textbook so many times too! What am I doing wrong? Homework Equations Zcapacitor = 1/(jwC) Zinductor = jwL Zresistor = R The Attempt at a Solution Z for the...
  47. J

    What does it mean to take positive rational numbers to whole

    What does it mean to take positive rational numbers to whole-number powers?
  48. ME_student

    Taking the derivative (no numbers)

    Homework Statement So I'd rather not type out the whole equation I am differentiating with respect to t... Sorry admins. My written work is on the image. I just want to make sure my work is correct. Homework Equations The equation is a differential characteristic equation with cos and sin...
  49. F

    Floor of ratio of Fermat numbers

    my turn to have something answered o0) 1. Homework Statement The problem is to show that Fermat numbers are relatively prime, which I could just look up somewhere but I want to use the mod operator that is used in Concrete Math, which says ##n \bmod m = n - m\lfloor{\frac{n}{m}}\rfloor## So if...
  50. A

    MATLAB MatLab: array of numbers unequal distribution

    I want to create an array of numbers between 0 and 0.1 where the points are clustered around an arbitrary point x1 (0 < x1 < 0.1). I want the points to get exponentially closer together near x1 from either side and and get further apart towards the outer limits. I am using MatLab and was trying...
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