What is Set: Definition and 1000 Discussions

Seth, in Judaism, Christianity, Mandaeism, Sethianism, and Islam, was the third son of Adam and Eve and brother of Cain and Abel, their only other child mentioned by name in the Hebrew Bible. According to Genesis 4:25, Seth was born after Abel's murder by Cain, and Eve believed that God had appointed him as a replacement for Abel.

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  1. R

    Prove/Disprove: p(a∩b) ≤ q^2 with a,b Independant

    Prove or disprove the following statement: If p(a)=p(b)=q then p(a∩b)≤q2 We know nothing know about event a , b. The Attempt at a Solution I tried this but don't know correct or not Can some one help me let a, b are independent event 0<q<1 then p(a∩b) = p(a) p(b) = q*q = q^2 [/B]
  2. P

    How to set the variation of an integral to 0?

    So I have an integral: ## \delta W=\int_{-\Delta}^\Delta\left[x^2\left(\frac{d\xi}{dx}\right)^2−D_S\xi^2\right]dx ## Here ##\xi## is a function of ##x## and ##D_S## is a constant. ##\Delta## is just some small ##x##. Now I need to set the variation of ##\delta W## to 0. Do do this I...
  3. M

    Does Intersection Distribute Over Subset in Set Theory?

    Homework Statement $$ A \subset B \Rightarrow A \cap C \subset B \cap C $$ 2. Homework Equations [/B] $$ A \subset B \Leftrightarrow A \cup B \subset B$$ $$ A \cap C \Leftrightarrow A \cap C \subset A \wedge A \cap C \subset C$$ The Attempt at a Solution For sets A and C $$A \cap C...
  4. H

    How to set the frequency of a switch in NI Multisim software

    I am a new user of Multisim and I am trying to make a buck converter. In other softwares, such as pspice I was able to control the switching frequency by editing properties but in Multisim, most of the switches are user interactive. I want to set frequency of 50 Hz in a switch. Kindly help me...
  5. 22990atinesh

    Prove Set Identity: A⋂(B⊕C)=(A⋂B)⊕(A⋂C)

    Homework Statement Prove that ##A\cap(B\Delta C)=(A\cap B)\Delta(A\cap C)## Homework EquationsThe Attempt at a Solution [/B] L.H.S.=##A\cap(B\Delta C)## =##A\cap[(B - C) \cup (C - B)]## =##A\cap[(B \cap \bar{C}) \cup (C \cap \bar{B})]## =##[A\cap (B \cap \bar{C})] \cup [A\cap (C \cap...
  6. T

    Are set theory functions sets too?

    I read somewhere that mathematical functions can be implemented as sets by making a set of ordered tuples <a,b> where a is a member of A and b is a member of B. That should create a function that goes from the domain A to the range B. But set theory has functions too, could they be sets too...
  7. JR Sauerland

    Set builder notation: is it ever used?

    Should I sharpen up on using set builder notation? Like, will I ever need it in physics or calculus? I'm currently refreshing my skill at writing in Interval notation for inequalities and the like.
  8. Physics-UG

    Programs Is this a good set up for my degree?

    So I was originally in Neuroscience and took a physics course and ended up loving it so much I switched over. Nonetheless, I'm pretty much starting from the beginning. I was wondering if this overall schedule throughout my degree would be good for potentially going into grad school for...
  9. H

    Prove that a finite set with cancellation laws is a group

    If G is a finite set closed under an associative operation such that ax = ay forces x = y and ua = wa forces u = w, for every a, x, y, u, w ##\in## G, prove that G is a group. What I attempted: If we can prove that for every x ##\in## G, x##^{-1}## is also ##\in## G, then by the closure of the...
  10. T

    MHB Outer measure exclusion of zero set question

    I've just started self-studying measure theory by reading Pugh's Mathematical Analysis. I'm trying to understand his argument for why the exclusion of a zero set does not change the outer measure: $m^*(E\setminus Z)=m^*(E)$: (Pugh's arugment): Let $Z$ be a zero set, $E\subseteq\mathbb{R}$, and...
  11. S

    Infimum and supremum of empty set

    Hello, I can't wrap my mind around this: inf∅= ∞ sup∅= - ∞ Thank you in advance.
  12. N

    Setting Up a RF Lab for Low Frequency DSP Projects | Nate Duong

    Dear everyone... I am trying to set up a RF lab at home to help me do DSP projects with very low frequency, as low as possible. Anyone who has experiences about RF lab, please give me some ideals and what machines from basic to advance will be needed for the lab? Thank you, Nate Duong.
  13. R

    Prove of number of subsets of a set

    Homework Statement A= {a1,...am}, B= {b1,...an}. If f: A→B is a function, then f(a1) can take anyone of the n values b1,...bn. Similarly f(a2). Then there are nm such function. I understand this part. So in my book, using this principle, nC0 + nC1 + ... + nCn = 2n is proved. It has taken a...
  14. Ryanodie

    Check my work on these proofs? (basic set theory)

    Homework Statement [/B] I am going through Apostol's Calculus volume 1 and am working through I 2.5 #3. I'm not very familiar with doing proofs so I just wanted to make sure that I got the right idea here. Here's the question: Let A = {1}, B = {1,2} Prove: 1. ## A \subset B ## 2. ## A...
  15. Rasalhague

    Proving that Every Closed Set in Separable Metric Space is Union of Perfect and Countable Set

    Homework Statement Prove that every closed set in a separable metric space is the union of a (possibly empty) perfect set and a set which is at most countable. (Rudin: Principles of Mathematical Analysis, 2nd ed.) Homework Equations Every separable metric space has a countable base. The...
  16. B

    Mathematica Plotting A Set of Points in Mathematica

    A have the set consisting of the complex numbers ##1 + 3r \cos \theta - i r \sin \theta##, where ## r \in [0,1]## and ##\theta## may vary between ##0## and ##2 \pi##. This is my first encounter with mathematica, and am having difficulty discerning between the methods I have found online which...
  17. CorvetteAB

    Want to set up a turbocharger for KTM 390 engine

    Hey friends, My college team takes part in college level racing events. They currently use a KTM 390 engine(race limit is 600). WIth the 20mm restrictor rule we can generate around 30-33hp after some tuning, after the restriction of course. Now we want more power. We need it. So we have 2...
  18. Ahmed Abdullah

    Why topology on a set is defined the way it is?

    Following is from Wolfram Mathworld "A topological space, also called an abstract topological space, is a set X together with a collection of open subsets T that satisfies the four conditions: The empty set is in T.X is in T.The intersection of a finite number of sets in T is also in T.The...
  19. evinda

    MHB Maximizing Independent Set in Graphs: Proving NP-Completeness

    Hello! (Wave) An independent set of a graph $G=(V,E)$ is a subset $V' \subseteq V$ of vertices such that each edge in $E$ is incident on at most one vertex in $V'$. The independent-set problem is to find a maximum-size independent set in $G$. Formulate a related decision problem for the...
  20. H

    Simplest lens set up to reveal optical spectra of an object

    I have done basic experiments where a laser is shot thru a grating and a lens is inserted at the diffraction pattern to put the spectra back together and form an image of the grating. apart from this being the single most mind blowing experiment ever to witness I have some questions about the...
  21. 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 =...
  22. B

    Injection from finite set to equally sized set is surjection

    This is a rather simple question, so it has been rattling my brain recently. Consider a surjective map ## f : S \rightarrow T ## where both ## S ## and ## T ## are finite sets of equal cardinality. Then is ## f ## necessarily injective? I proved the converse, which turned out to be quite...
  23. Keen94

    Truth Set for the given Equivalence

    Homework Statement Find the truth set of the given equivalence. Assume U=ℝ #56. (x2=1)↔[(x=1)∨(x=-1)] Source: Principles of Mathematics by Allendoefer and Oakley section 1.10 Homework Equations {x I px↔qx}=(P∩Q)∪(P'∩Q')[/B] The Attempt at a Solution P={x I px}={x I x2=1}={x I x=1 or -1)...
  24. Keen94

    Finding the Complement of a Set

    1. Find P'={x I ~px} for the given open sentences px. #25. x2≥4. (Problem from 1.10, Principles of Mathematics by Allendoerfer and Oakley. Solution offered at the back of the book: {x I -4<x<4}.Homework Equations If P={x∈ℝ I px} then P'={x∈ℝ I ~px}[/B]The Attempt at a Solution x2≥4 ⇒ x≤-2 or...
  25. B3NR4Y

    Simple Set Theory Proofs: A Guide to Proving Set Identities - Homework Help

    Homework Statement 1. Prove that if A \cap B = A and A \cup B = A , then A = B 2. Show that in general (A-B) \cup B \neq A 3. Prove that (A-B) \cap C = (A \cap C) - (B \cap C) 4. Prove that \cup_{\alpha} A_{\alpha} - \cup_{\alpha} B_{\alpha} \subset \cup_{\alpha} (A_{\alpha} -...
  26. B

    Set theory, intersection of two sets

    Homework Statement We have the set D which consists of x, where x is a prime number. We also have the set F, which consists of x, belongs to the natural numbers (positive numbers 1, 2, 3, 4, 5..) that is congruent with 1 (modulo 8). What numbers are in the intersection of these two sets...
  27. Spinnor

    Set of postulates implies postulates of Q.M.?

    Is it possible that there is a set of postulates (or statements) whose logical implications imply the quantum nature of our Universe, the postulates of quantum mechanics? Could there be more than one set? Thanks for any help!
  28. nomadreid

    Anomaly set theoretic equivalent to material implication

    OK, this is embarrassing, but I never looked carefully at this elementary point. We say that if p implies q P is the set of all things for which p is true Q is the set of all things for which q is true then Q ⊆ P. Also that the set of all things for which p&q is true equals P∩Q But p & q...
  29. Jaco Viljoen

    Find the solution set of 2^(2x-2)-2*2^(x-1)=8

    Homework Statement Find the solution set of 2^(2x-2)-2*2^(x-1)=8 Homework EquationsThe Attempt at a Solution 2^(2x-2)-2*2^(x-1)=8 2^(2x-2)-2^(x-1+1)=8 2^(2x-2)-2^(x)=8 2^(2x-2)-2^(x)-8=0 2^(2(x-1))-2^(x)-8=0 I cannot solve the equation, I just need direction with this step and will attempt...
  30. J

    Titration Lab Equipment Set Up

    Homework Statement Hi everyone. I'm teaching introductory chemistry this semester, but I don't have much of a chem background. We are about to start acid base titrations. Does the standard solution of known concentration go in the buret tube or the erlenmeyer flask? Does it matter? Homework...
  31. R

    MHB Finding Two Points in a Convex Set: Help Needed!

    I have two a convex set: {(x1, x2): 1≤ ∣x1∣ ≤2, ∣x2−3∣ ≤ 2} I have to find two points in the set for which the line segment joining the points goes outside the set. I have graphed the function and found my convex set. My question is, how do I find these two points? I have found various points...
  32. UncertaintyAjay

    Prob/Stats Axiomatic Set Theory: Book Recommendations?

    So I just finished "Book of Proof" and I'm looking for a more rigourous book on axiomatic set theory, including Gödel's theorems.Any recommendations?
  33. R

    Finding value in a complex set region

    Homework Statement The largest value of r for which the region represented by the set { ω ε C / |ω - 4 - i| ≤ r} is contained in the region represented by the set { z ε C / |z - 1| ≤ |z + i|}, is equal to : √17 2√2 3/2 √2 5/2 √2 Homework Equations complex number = a + ib where a,b ε R The...
  34. I

    Tangential force acting on a skier has been set to zero?

    Can anyone explain why sum of Ft has been set to be = 0? The slope is smooth so no frictional forces act but by setting it to 0 they are neglecting the component of the weight along the slope? Having said that, this is a curved slope and not a straight one so does the component of the weight...
  35. M

    Researching Set Theory as an Undergrad

    I'm currently an undergrad in math who's going to graduate next year. I'm interested in doing research in set theory (not now of course, perhaps in grad school). Unfortunately, I'm at a liberal arts school and there are no set theorists in the math department. All they offer is a naiive set...
  36. ognik

    MHB Can a vector space also be a set?

    Wiki says "A vector space is a collection of objects called vectors, which may be added together and multiplied ("scaled") by numbers, called scalars in this context." To me the term (linear) Vector Space has always seemed a little mysterious ... how far wrong would I be in thinking of a vector...
  37. R

    Comp Sci Java: Set Interface Homework - Avoid Overriding Methods

    Homework Statement If I have a subclass that implements a set class how can I avoid having to override all the set classes methods? Homework Equations None The Attempt at a Solution I have an interface: import java.util.Set; /** * An extended Set where there is added...
  38. nuuskur

    Proof: open ball is an open set

    Homework Statement Second try at the proof, this time with correct vocabulary, I hope Prove that an open ball is an open set. Homework EquationsThe Attempt at a Solution Let B(P_0, r) be an open ball in \mathbb{R}^m, where P_0 is the centerpoint of the ball and r > 0 is its radius. Assume...
  39. nuuskur

    Proof: open sphere is an open set

    Homework Statement Prove that an open sphere in \mathbb{R}^m is an open set. Homework EquationsThe Attempt at a SolutionTo show that an open sphere is an open set, any point inside the sphere has to be an interior point: Let us have a sphere B(P_0, r), r > 0, where P_0 is the centerpoint and r...
  40. C

    Quantum Mechanics is a set of Laws

    Hi, I know this is a basic question however, I am seeking absolute verification on these two points. 1) Quantum Mechanics is a set of Laws. 2) Laws only describe what we see. Theories give us the reason behind them.
  41. J

    Proof that the set of stationary states are orthonormal?

    Hello there, I am just starting quantum physics with the textbook by griffiths. My lecturer has told me that the set of functions representing stationary states in Hilbert space forms an orthogonal set. He was however unable to prove it. Furthermore he said that it is not always the case, but...
  42. Math Amateur

    MHB Inverse image of a set under the restriction of a function

    I am reading Munkres book, "Topology" (Second Edition). I need help with an aspect of Theorem 18.2 Part (f) concerning the inverse image of a set under the restriction of a function ... Theorem 18.2 Part f reads as follows: In the above text we read: " ... ... Let V be an open set in Y...
  43. A

    Teacher told to set absolute value inequality to equal 0

    So I was helping my sister on homework and there was this problem: 2 abs(2x + 4) +1 > or equal to -3 teacher told her to ignore the -3 and just set it equal to zero. Soo should you? This question got me confused. can't you just go about solving, bringing the 1 to the left and then dividing by 2...
  44. C

    MHB Surjective functions from a set of size n+3 to a size of n

    Hello, I wonder if anyone could settle a disagreement I'm having with one of my peers. The question is 'How many surjective functions are there from a set of size n+3 to a set of size n?'. Now, I've already proven that there are (n+1 choose 2)n! surjective functions from a set of size n+1 to a...
  45. DaveC426913

    Simple statistical analysis of a limited data set

    I should have studies statistics in school. I have been collecting some trip data from you commute to and from work, and I want to determine what factors are influencing trip duration. There are multiple factors, which I cannot easily isolate. The factors I'm most interested in are: - duration...
  46. R

    Paralleling a Diesel Generator Set

    I have seen many establishments having a backup electric supply using a Diesel Generator Set (AC / 3 phase). e.g. Something like in the Photo Below. What happens if the connected load grows beyond the capacity of a single generator? e.g. The unit in the photo is rated for 200 kVA. Suppose the...
  47. K

    MHB Uniform convergence of a complex power series on a compact set

    I need to prove that the complex power series $\sum\limits_{n=0}^{\infty}a_nz^n$ converges uniformly on the compact disc $|z| \leq r|z_0|,$ assuming that the series converges for some $z_0 \neq 0.$ *I know that the series converges absolutely for every $z,$ such that $|z|<|z_0|.$ Since...
  48. Spinnor

    Set of points in S^3, way to show spaced equal or not?

    In an earlier post here I wanted to chop up a three-sphere into cubes, Ben suspected it was not possible and I have no reason to think otherwise. From earlier help by Fezro, here, I may be able to move this forward. Assuming the posts by Fezro are correct I think I can come up with a set of...
  49. AlephNumbers

    Solve Set Theory Question: Can Countably Infinite Set Have Uncountable Subsets?

    Lately I have been attempting (and failing miserably at) whatever sample Putnam questions I can find on the internet. Here is my latest endeavor. I found this question on the Kansas State University website, so I think I am allowed to post it. I must warn you that I know almost nothing about...
  50. xwolfhunter

    Question about empty sets in set theory

    So I'm reading Naive Set Theory by Paul Halmos. He asks: His response is that no ##x## fails to meet the requirements, thus, all ##x##es do. He reasons that if it is not true for a given ##x## that ##x \in X~ \mathrm{for ~ every} ~X~ \mathrm{in} ~ \phi##, then there must exist an ##X## in...
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