Recent content by Russell Berty

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    Find the Error: Differentiation

    :approve: Which, of course, we have D(x times) = (1 times), so... D(x + x + ... + x (x times)) = (1 + 1 + ... + 1) (x times) + (x + x + ... + x) D(x times)= (1 + 1 + ... + 1) (x times) + (x + x + ... + x)(1 times)= x + (x) = 2x
  2. R

    Find the Error: Differentiation

    That is a cute one. :tongue2: But... (1 + 1 + ... + 1) "x times"? The right hand side is only defined for non-negative integer values of x. How can you write the symbol 1 "x times" when x is 1.5, or square root of 2, or pi? How can you add 1 to itself "x times" when x is pi? If you...
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    What Costs More the More You Buy?

    One will cost you $.25. Fifty will cost you $.50. One hundred will cost you $.75. What is for sale?
  4. R

    People who do foundations of maths?

    :rofl: Perhaps a weaker axiom would suffice: 0\approx1 or 0\in0
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    Can an individual truly assert their existence through thought alone?

    We can assert individually that “I exist” as well as “thinking exists.” But our assertions may not be valid. “Thinking exists” is an extremely reasonable assumption. However, “thinking exists” is not known to be true beyond all possible doubt. Playing the skeptic game is very useful...
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    Why is this proof wrong?

    We are dealing with antiderivatives. So, given F(x) and G(x) that are antiderivatives of 1/x, it is true that F(x) = G(x) + C, for some constant C. For example, the second to last line you have can be written as ln(x) + C = 1 + ln(x) + D for some constants C, and D. We do not then...
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    Range space of linear mappings

    Hints: For part a: Note that the range of M is a subspace of Rp with dimension Rank(M). Likewise, the range of L is a subspace of Rm with dimension Rank(L). For the composition ML, notice that after L is applied, the range of L is not necessarily all of Rm. Moreover, when you next apply...
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    # of intersections for 2 curves on a plane

    Choosing an arbitrary element from a set is a random process. Choose an element from the set {1,2,3,4,5}. What is the probability that the element is the number 4? 1/5. My “choice” is random in the probabilistic sense. If it was not, I cannot conclude the probability of choosing 4 is 1/5...
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    # of intersections for 2 curves on a plane

    I only said that it sounds like a random walk problem. That is, it has that same flavor. I am sorry to have mentioned random walks. I was primarily trying to simplify the original question to “what is the probability that a curve intersects itself?” In fact, I am still uncertain what the...
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    Solve the "Hardest Logical Puzzle Ever

    When looking at the case where the gods speak English (Yes or No responses), here is another hint. Hint: The first question has the following form. “Is it true that (p and q) or (w and v)?” Where p, q, w, v are simple statements. From the response to this question, you should be able...
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    # of intersections for 2 curves on a plane

    I am assuming that you do not necessarily mean “graph of a function” when saying “curve”. So a curve can cross itself. So an easier question to ask is “What is the average number of times a curve intersects itself?” This sounds like a random walk problem. So, one could try to answer the...
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    Unraveling the Right Angle Proof of Derivatives of Inverse Trig Functions

    Speaking of the square root of two… Here is a fun little nonconstructive existence proof. Prove that there exists irrational numbers a and b such that a^b is rational. Proof – Note that \sqrt{2}^{\sqrt{2}} is either rational or irrational. We will argue by cases. Case 1) If...
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    Why Does the Hadamard Function Imply Imaginary Numbers?

    I believe, historically, i was introduced to name a solution to x^2 = -1. I don't know if this is what you want, but here is a “real world” interpretation of i. In the real world, we have the idea of marking a central point on a line (call it 0.) Then we can mark evenly spaced units along...
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    Challenging problem corrrection no sine and no cosine law

    Label the following unknown angles: a = BDF b = FDC c = DEF d = FEC e = BFD f = DFE g = EFC Then, write 7 different equations involving them. For example, a + e + 140 = 180. Once you have 7 equations with 7 unknowns, it can be solved. Though, it is messy. If you know...
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    Is infinity a constant or a variable ?

    In keeping with the original question of this post, I believe there are some other concepts that need clarifying (not merely “infinity”.) What is a constant? What is a variable? These also need to be understood from context. From the question it sounds like the underlying context is the set...
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