1. J

    Relational Thinking (functions)

    Hi, I'm taking essential of discrete mathematics for college. I'm using David Hunters book. In chapter 2 of relational thinking 2.3 functions problem 8. Consider Example 2.23. Let y be some person. What is the relationship of (mom)(y) to y? Example 2.23 is Let P be a set of all people...
  2. M

    Relational Notation - Domain and Range restriction help required

    I have a question from an exercise that I am struggling with or to get grips with. I have to write all of them in relational notation in terms of drives etc etc. Sorry I cannot post my solutions to the other questions to show you exactly what I am trying to achieve. Here is the question, I have...
  3. S

    relational expression, zermelo definition, proper divisor...

    Q) [/B]Consider the predicate D : N × N → {T, F} (N stands for the natural numbers) where D(x, y) means ‘x is a proper divisor of y’. (a) Write a boolean expression for D(x, y), using relational expressions and boolean operators. (b) Let E be the set of even natural numbers which are...
  4. J

    translation to relational symbol sets (From "Mathematical Logic" Ebbinghaus, et al)

    if anyone has the book "Mathematical Logic" by Ebbinghaus, Flum and Thomas, I'd like to check if the pf of thm 1.3 on pg 117 is correct. I don't think it is. In the pf of part (a)we're not told anything about possible S-formulas where constant symbols appear. The pf of equivalence would be...
  5. M

    relational algebra

    for the question: Assume that R and S are relations on a set A. Prove (using relation-algebraic calculations) or disprove (by providing counterexamples) each of the following statements. a) If R and S are both reflexive, then R ∪ S is reflexive, too. how would i start to answer this question...
  6. T

    Relational proof

    If R is reflexive and transitive, then R U R^U is an equivalence. I need to prove this using algebraic-relation calculations or disprove by counter example. I'm really not understanding this stuff. (Worried)
  7. T

    Prove with relational algebra

    If R and S are both reflexive, then R ∩ S is reflexive, too. I need to prove this with relational algebra or disprove by giving a counterexample. Any help? (Rock)
  8. B

    (Discrete Mathmatics) Defining a relational set

    The problem is this: Let A be the set of integers and let n be a fixed positive integer. Define a relation on A be saying xRy if n divides x - y or x + y. Just giving an example, if n = 5 we know 3R7 since 5 divides 3 + 7 = 10. Also it works with 12R2 12 - 2 = 10. Prove R is an equivalence...
  9. I

    Relational Composition Problem - Please help!

    Hi, I have a problem which says this: Prove that if r;s is reflexive, then r is total and s is surjective. Thanks.