Recent content by Susanne217

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    Are Statements 1 and 2 Logically Equivalent in All Contexts?

    I am not sure what you are trying to say here?? 1) There exists an x and then P(x) results in M(x)? You say something more about x in order to use these symbols. Like there (\exists x \in A(x) \Rightarrow A(x) \mapsto M(x)
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    Infinite series (i think it's riemann)

    Then I have made a mistake cause it get to be 0.373551 and not a 1/3 :(
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    Infinite series (i think it's riemann)

    Isn't it true that you need to rewrite this series into more easy to work with??
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    Finding a continous solution to an integral

    Am I right this is complex analysis?
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    Infinite series (i think it's riemann)

    I agree... I have been away for a while but I think it could be that the young man is suppose re-write the sum to an improper integral and thereby finding the sum of the series??
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    Infinite series (i think it's riemann)

    Isn't it suppose to be \sum_{n = 1}^{\infty} \frac{k^2}{n^3 + k^2}
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    Find the solution of the equation using a given f(x)

    Homework Statement I have the heat equation \frac{\partial u}{\partial t} = k \frac{\partial^2 u}{\partial x^2} where u(x,0) = f(x) and f(x) = \frac{sin(x)}{x} use the expression of the Fourier Integral to calculate u(x,t). Homework Equations The Attempt at a Solution Do...
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    Natural log's and trigonometric identity's.

    Oh well, I am sure that Jedi Hal will find this post and correct us all, but that said I learned in High School x^{-1} = \frac{1}{x} which implies e^{-x} = \frac{1}{e^x} thus e^{-ln(x)} = \frac{1}{e^{ln(x)}} = \frac{1}{x} Use this property to prove you problem, OP!
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    Natural log's and trigonometric identity's.

    you forgot an important fact e^{-ln(x)} = \frac{1}{x} If he/she uses that fact then it explains the rest :)
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    Solving a very strange improper integral

    Homework Statement I am getting fooled by the this improper integral \int_0^{\infty}\frac{cos(x)+sin(x)}{1+v^2}dv = \pi \cdot e^{-x} How the devil do I go about getting that result? The Attempt at a Solution I end up getting the sum of the two integrals...
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    Is ln(n) Less Than n^c for All c>0 and n>N?

    I think that you can do it like this: If you view these two function as series e.g. \sum_{n=1}^{\infty} ln(n) and \sum_{c=1}^{\infty} n^c and then use the comparison test from Calculus to show that ln(n) < n^c
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    Proving Determinant(AB)=det(A)det(B)

    You are right :) a_1, a_2, \cdots a_n are row in the matrix A. I also forgot to mention for this be allowed then A and B must live up to the row column rule :)
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    Prove x^3 - y^3 = (x - y)(x^2 +xy + y^2)

    It sure was Hall, but I had a feeling that original poster didn't know that if you have (a+b)(a+b)= a^2 + ab + ab + b^2 It hard to be young these days!
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    Does AB = I Imply BA = I for Square Matrices?

    HallsofIvy, I know you have the ability to use the force at a higher level than the rest of us. But the assigment does say "Show that if AB = I, then also BA = I, so A and B are invertible." In my opinion it all comes down to how you read the problem at hand. 1) For A and B to...
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    Prove x^3 - y^3 = (x - y)(x^2 +xy + y^2)

    This isn't hard if you expand the RHS. x^3 + x^2y + xy^2 - x^2y - xy^2 - y^3 and the rest easy...
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