Recent content by Chicago_Boy1

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    Don't understand why this set is bounded

    Hey all, We were discussing bounded and unbounded sets in class, and looking over my notes, I see that I have some trouble understanding the concept. Here are three examples that our professor gave us: Set A = {x\inR | |x| <10} Set A = {x\inR | x<10} A\subseteqZ s.t. x~y iff x|y Set A =...
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    Derivative of a partial derivative

    Hello, So I have the function U(x,y). I have to find a partial derivative of U with respect to x. I understand that one can write that as U subscript x. But now I have to take d/dx of Ux, i.e. I have to take the derivative of Ux(x,y) with respect to x. Supposedly the answer is Uxx +...
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    Fundamental Counting Principle Proof (NOT via induction)

    Hello all, I am going through some sample problems exercises in Paul Sally's Tools of the Trade, and am being asked to prove the Fundamental Counting Principle. That is, If A has m elements and B has n elements, then A X B has mn elements. Sally goes on to write that "this is simple to prove...
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    Can Proofs Involving the Empty Set Be Solved by Contradiction?

    Would that be for the first part or the second part? Sorry, I am just a little confused...
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    Can Proofs Involving the Empty Set Be Solved by Contradiction?

    Thanks for the tip. I'll be more careful with my terms next time! I guess I am a little confused by your note that it is useful to observe that A \subset A \cup B and B \subset A \cup B. How exactly does it fit into the problem?
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    Can Proofs Involving the Empty Set Be Solved by Contradiction?

    I am doing some non-homework exercises in preparation for my midterm, and am struggling with the following proofs: First Prove {} is a subset of {}, where {} refers to an empty set My professor told me to do this by contradiction. So I assume that {} is not a subset of {}. That would imply...
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