Set Definition and 1000 Threads

  1. Silicon Waffle

    Windows Server 12 R after DNS set up

    After I installed a fresh windows server 2012R, I could log in with administrator account, e.g MYWIN\Administrator (MYWIN is my computer name). Then I created a DNS/forest e.g ABC.com , I then could log in with ABC\Administrator. For some reason I now sign out and would want to log in with...
  2. PengKuan

    Cardinality of the set of binary-expressed real numbers

    Cardinality of the set of binary-expressed real numbers This article gives the cardinal number of the set of all binary numbers by counting its elements, analyses the consequences of the found value and discusses Cantor's diagonal argument, power set and the continuum hypothesis. 1. Counting...
  3. G

    Number of partitions for a finite set

    Homework Statement Find a recursive relation on the number of partitions ##P_n## for a set ##S_n## of cardinal ##n##. ##P_0 = 1## is given. Homework EquationsThe Attempt at a Solution A partition of ##S_{n+1}## is given by the choice of a non-empty ##k##-block ##A_k## of ##S_{n+1}## and a...
  4. T

    Proving Compact Set Exists with m(E)=c

    Homework Statement Suppose E1 and E2 are a pair of compact sets in Rd with E1 ⊆ E2, and let a = m(E1) and b=m(E2). Prove that for any c with a<c<b, there is a compact set E withE1 ⊆E⊆E2 and m(E) = c. Homework Equations m(E) is ofcourese referring to the outer measure of E The Attempt at a...
  5. S

    The set consisting of random numbers with random lengths

    Does the set of random integers with random lengths (the number of digits), which hypothetically would generate random numbers with random lengths for eternity, produce all possible integers? It seems to me that this is a natural conclusion but I've never seen a proof of this. A more incredible...
  6. Gh. Soleimani

    I Are These Rules new Conjectures in Set Theory?

    We can easily find out below rules in set theory: 1. Let consider set “A” as follows: A = {a1, a2, a3, a4… an} and also power set of A is set C: C = {{}, {a1}, {a2}, {a3}, {a4}, {a1, a2}, {a1, a3},….{an}} Rule 1: To find the number of subsets with precise members number, we can use Binomial...
  7. M

    Can a Finite Set of Vectors Form a Subspace?

    Homework Statement \begin{pmatrix} 1 & 1 & 0 & 0 \\ 0 & 1 & 1 & 0 \\ 0 & 0 & 1 & 0 \end{pmatrix} Is this set a subspace of ℝ3 Homework Equations The set must be closed under addition. The set must be closed under multiplication. The set must contain the zero vector. The Attempt at a...
  8. qq545282501

    Did I set up my integral correctly?

    Homework Statement use triple integral to find volume of the solid in the first octant that is bounded above by x+2y+3z=6 and laterally by the clyinder x^2+y^2=4 Homework EquationsThe Attempt at a Solution From the given plane I got: Z=2-\frac{1} {3}x-\frac{2} {3}y from the given Cylinder i...
  9. qq545282501

    Did I set up my integral correctly?

    Homework Statement use spherical coordinates to find volume inside a sphere of radius 4 and outside sphere of radius 2, and inside/above the cone z=3√(x^2+y^2). Homework Equations [/B] x=rcosθ =ρsinφcosθ , y=rsinθ =ρsinφsinθ z=ρcosφ r= ρsinφ The Attempt at a Solution replacing z^2 in the...
  10. Z

    Why Does the Set {1/n : n ∈ ℕ} Have an Empty Interior?

    Hi All, A simple question but one for which I cannot seem to get the intuition. 1. Homework Statement Find the interior point of {1/n : n ∈ ℕ}. Homework Equations N/A The Attempt at a Solution Let S = {1/n : n ∈ ℕ}, where S ⊆ℝ x is an interior point if ∃N(x ; ε), N(x ; ε) ⊆ S. My...
  11. J

    Looking for book on ZFC axiomatic set theory (I think)

    I am looking for a book that starts at the standard ZFC axioms and progresses to the point where some recognisable non-trivial mathematical statement is proved. By recognisable I mean something that you may encounter in school/early university level and is not purely set-theoretical (e.g...
  12. P

    Understanding the Closed Set of Natural Numbers

    Hi, How and why set of natural numbers is closed?
  13. W

    Help understanding a set and its distribution

    Homework Statement given set C = {(x,y)|x,y are integers, x^2 + |y| <= 2} Suppose they are uniformly distributed and we pick a point completely at random, thus p(x,y)= 1/11 Homework Equations Listing it all out, R(X) = {-1,-2,0,1,2} = R(y) The Attempt at a Solution My problem is that when I...
  14. K

    Soln: Acceleration of System & Tension in Ropes

    Homework Statement Find the Acceleration of the system and the tensions in the three ropes. *If you can't see the picture there's a triangle (ABC), a train of four objects and three pulleys (one exactly at each corner). Side AC (hypotenuse) at the bottom, side AB to the left and side AC to the...
  15. Z

    How many elements does the set A union B have?

    Homework Statement A and B are both spans. A = span(a1,a2,a3) B = span(b1,b2) Then how many elements would AUB have? Homework Equations N/A The Attempt at a Solution [/B] I'm almost certain the answer is 2, with the two elements being span(a1,a2,a3) and span(b1,b2) but I'm unsure as to...
  16. H

    How do we orbit the sun when you can set your origin anywhere....

    As I understand it a coordinate origin is just chosen for convenience. So how can we state the Earth revolves around the sun when you could make coordinate origin at any point in the universe??
  17. G

    I Frame-Independent Set of Events?

    In SR, an event is a particular point in space and time.For simplicity, we only use one dimension of space. We have x'=γ(x-vt) if when x, t = 0 , x', t' = 0Let's say we have a bunch of inertial frames, all moving at different speeds, but all sharing a common origin x, t = 0 From the POV of...
  18. M

    Dimension of the span of a set of vectors

    My linear algebra is a bit rusty. Let ##A=\{\bar{v}_1, \dots, \bar{v}_1\}## be a set of vectors in ##R^n##. Can dim(span##(A))=n## without spanning ##R^n##? I guess I'm unclear on how to interpret the dimension of the span of a set of vectors.
  19. astrololo

    Why do we need the set of complex numbers to solve?

    I was wondering, why is the set of complex numbers needed to solve problems that the set of reals doesn't permit to ? I mean, in relation to the fundamental theorem of algebra, that is.
  20. ShayanJ

    Complete set of multi-variable functions

    We know that in the space of functions, its possible to find a complete set so that you can write for an arbitrary function f, ## f(x)=\sum_n a_n \phi_n(x) ## and use the orthonormality relations between ## \phi##s to find the coefficients. But is it possible to find a set of functions ##...
  21. Antonius

    Parametrize the solution set of this one-equation system.

    The question: Parametrize the solution set of this one-equation system. x_1 + x_2 + ... + x_n = 0 My question (please look at the photo): I understood why we have the first row, but what's the point of the other rows?
  22. J

    Largest set on which the function is analytic

    Homework Statement Determine the largest set on which the function is analytic. f(z) = (z2-2)e-xe-iy Homework Equations z=x+iy f(x+iy) = U(x,y) + iV(x,y) Ux=Vy Uy=-Vx The Attempt at a Solution I think I'm right in saying that f(z) is analytic if the CR equations (provided above) are...
  23. C

    Is there a simpler way to solve this Venn diagram algebra problem?

    Homework Statement I solved the problem myself but i have a question about the algebra Homework Equations n(A ∪ B ∪ C) = n(A) + n(B) + n(C) -n(A ∩ B) -n(A ∩ C) -n(B ∩ C) + A ∩ (B ∩ C) = n(A ∪ B) -n(A ∩ C) -n(B ∩ C) + A ∩ (B ∩ C) The Attempt at a Solution I knew i needed...
  24. gfd43tg

    Membrane separations experimental set up

    Hello, I will be doing an experiment to separate N2 from O2 in air using membrane separations. I need to write my own experimental procedure to find the objectives of the experiment. Here is our experimental set up I'm trying to figure out how to do objective i. I need to figure out the...
  25. S

    A "neat set of reactions" that makes fuel on Mars

    Hi, I'm reading The Martian by Andy Weir (fantastic book). A character, describing how a Mars mission works, says of fueling their ascent vehicle: "Through a neat set of chemical reactions with the Martian atmosphere, for every kilogram of hydrogen you bring to Mars, you can make thirteen...
  26. V

    Understanding the Standing Wave Equation for Students

    Homework Statement Homework Equations y (x,y) = 2YmSin(kx)Cos(wt)The Attempt at a Solution I am having trouble at setting up the standing wave equation for this problem. Once I set up the equation, I know that part a b c d is just plugging in the numbers. From what I learned, I know that...
  27. D

    Java Java- Set hasDigit to true if the 3-character passCode contains a digit.

    Been working this problem for hours and can't seem to get it right. Any assistance would be greatly appreciated! Note: Green colored text is the editable text public class CheckingPasscodes { public static void main (String [] args) { boolean hasDigit = false; String passCode =...
  28. yango_17

    Determining whether a set is open, closed, or neither

    Homework Statement Determine whether the given set is open or closed (or neither): {(x,y,z) ε R^3, 1<x^2+y^2<4} Homework EquationsThe Attempt at a Solution I believe that the set is open due to the only bounds being inequalities that are less than, not less than or equal to, but that seems...
  29. O

    MHB Cardinality of Set A: 1 or $\le$1?

    Suppose that set A have unique element...Can we say that cardinality(A)=1 or $cardinality(A)\le1$ ? Which one is true ?
  30. 1

    Finding the set of u such that

    Hi. I'm having trouble understanding the logic behind finding a set of u for u(u-1) > 0. To solve these, I tend to factor as much as possible, then equate each expression to 0 (in this case to > 0) and solve, changing the > to < if I must divide by a negative number. I get u >0 and u > 1 but the...
  31. F

    MHB Next set of prime birthdays for three brothers

    Hello! I have the following problem: Three brothers are aged 6, 10 and 14 years old. Will they ever, in the future, have a prime number birthday the same year? Looking at all of the prime numbers between 1 and 100, it seems that they won't. So I guess this is the same thing as saying: are...
  32. Math Amateur

    MHB Coordinate ring of an affine algebraic set - k[A^n]/I(V)

    I am trying to gain an understanding of the basics of elementary algebraic geometry and am reading Dummit and Foote Chapter 15: Commutative Rings and Algebraic Geometry ... At present I am focused on Section 15.1 Noetherian Rings and Affine Algebraic Sets ... ... I need someone to help me...
  33. Math Amateur

    MHB Arbitrary Subset of A^n - Is it necessarily an affine algebraic set?

    I am trying to gain an understanding of the basics of elementary algebraic geometry and am reading Dummit and Foote Chapter 15: Commutative Rings and Algebraic Geometry ... At present I am focused on Section 15.1 Noetherian Rings and Affine Algebraic Sets ... ... I need someone to help...
  34. MathematicalPhysicist

    A path which its domain is a general compact set.

    How is a general path called instead of being a continuous function from an interval to some topological space, where we replace the domain from an interval to a compact set, is there a name for such a function? Perhaps I should add that the compact set is also convex.
  35. J

    What does vertical bars around a set mean?

    I'm trying to figure out what the vertical bars in |A∪B| mean given that A and B are both sets. I tried searching for it, and can't seem to find the meaning of it. Is it supposed to be absolute value of all the elements of the union of sets A and B?
  36. J

    Normalizer N_G(X) equal to another set when o(X)<infty

    1. The problem statement, all variables and given/known Prove that if a set ##X\subseteq G## is finite then it's Normalizer in G, ##N_G(X)## is also equal to the set: ##A=\{g\in G : gXg^{-1}\in X\}## Homework Equations Given ##X\subseteq G##, then the normalizer of X in G is defined as...
  37. StevieTNZ

    News Queen Elizabeth II set to become longest reigning UK monarch

    http://www.stuff.co.nz/world/europe/71871827/queen-elizabeth-ii-set-to-become-longest-reigning-uk-monarch
  38. C

    Can the entries of a Matrix be elements of an unordered set?

    Most definitions of a matrix that I have seen involve entries that are elements of a field. What if I have a unorderd set with no operations defined on it, say a set of different colored marbles or a set of historical events. Can I have a matrix whose entries are elements of such a set?
  39. Ahmad Kishki

    Closed Set Proof: Show Limit Points of A is Closed

    Homework Statement Show that the set of limit points of the set ##A \subseteq \mathbb{R}## given by ##L## is a closed set.2. Relevant theorems Definition: A closed set F (subset of R) is such that it contains its limit points. Definition: A limit point x of a set A (subset of R) is such that...
  40. H

    Solving Set Equality Proof Homework

    Homework Statement Let ##A, B, C## be sets with ##A \subseteq B##. Show ##(A-B)\cup C=(A\cup C)-(B\cup C)## Homework Equations None. The Attempt at a Solution So, generally, one shows two sets to be equal by showing that each is a proper subset of the other. I started with the LHS. Thus...
  41. W

    Set Theory, Rough Set Theory, Fuzzy Set Theory

    Hi. I hope this is not too far into philosophy. Set Theory is commonly accepted as the foundations of Mathematics. Is it possible to develop a different type of Mathematics by using Fuzzy sets or Rough sets instead?
  42. W

    Probability, Set Theory, Venn Diagrams

    Homework Statement Let A and B be two events such that P(A) = 0.4, P(B) = 0.7, P(A∪B) = 0.9 Find P((A^c) - B) 2. Homework Equations I can't think of any relevant equations except maybe the Inclusion Exclusion property. P(A∪B) = P(A) + P(B) - P(A∩B) This leads us to another thing P(A∩B^c)...
  43. DeldotB

    Set Theory: Prove a function is injective

    Homework Statement Hello, I need some help on the following. I am BRAND new to set theory and this was in my first HW assignment and I am not sure where to start. The question is as follows: Let A and B be parts of a set E Let P(E)\rightarrow P(A) X P(B) be defined by f(X)=(A\cap X,B\cap X)...
  44. C

    MHB Solving Linear Equations: 2 Planes from LAX - Cbarker1

    Dear Everyone, I have some help setting up a system of linear equation. The problem states, Two planes start from Los Angeles International Airport and fly in opposition directions. The second plane starts $\frac{1}{2}$ hour after the first plane, but its speed is 80 kilometers per hour...
  45. A

    Best straight line fit to a set of data

    Hello, I didn't know where to put my question, but I think here is the best section for it. http://im60.gulfup.com/apkrpJ.png The problem isn't that I can't solve it, I actually did but I don't understand the concept ! -- I don't remember anything from my high school stat and I didn't do...
  46. B

    Does Minimum of Complex Set Subset Exist?

    Homework Statement The following doesn't come from a textbook, and I am very uncertain whether it is true or false. Suppose that ##B \subseteq \mathbb{C}## is a convex set, and consider the set ##L_B := \{|b|: b \in B \}##. Homework EquationsThe Attempt at a Solution My question is, will...
  47. K

    Ansys Maxwell: Set solution context error

    I have to created a Current Transformer by Ansys Maxwell 15. I set Boundaries, Excitations, Mesh Operations, and Analysis correctly. Finally, I select the menu item View > Set Solution Context, the Set View Context is appeared, and I want set Time to "0s" but it shows only "-1". I don't...
  48. ELB27

    Tensor products: different sizes of apparently the same set

    Homework Statement Show that the set ##\{\mathbf{v}_1⊗\mathbf{v}_2⊗...⊗\mathbf{v}_p:\mathbf{v}_k\in V_k\}## of tensor products of vectors is strictly less than ##V_1⊗V_2⊗...⊗V_p##. Homework EquationsThe Attempt at a Solution Truly, I don't see any difference between the sets. They seem...
  49. davidbenari

    Why is the set of cosines and sines a vector space?

    So when I took linear algebra I was asked to show the well-known properties of orthogonality in the functions cos(mx) and sin(mx)... With this I mean all the usual combinations which I don't see why I should point out explicitly. The inner product in the vector space was defined...
  50. K

    Solving this set of trigonometric equations

    I have the following set of equations from which I need to find δ and φ uniquely (i.e without quadrant ambiguity). In other words I need to have expressions for tan δ and tan φ involving A,B,C and D which are known quantities. A=1-sin(squared) δ/2 x sin 4φ B=1+sin(squared) δ/2 x sin 4φ C=...
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