Recent content by physics4life

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    How can I find the maximum value of a function on a specific interval?

    how would i find something like: max[\frac{x}{2} + cos(x)] where x\epsilon [0,\pi] and ... max[\frac{x}{2} + cos(x)] where x\epsilon [-\pi,0] ------------------------------------------- here's what i did for max[\frac{x}{2} + cos(x)] where x\epsilon [0,\pi]: first we need critical...
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    Vector Calculus Subscript Notation

    im actually getting the hang of it now. but stuck on dot product of cross products.. e.g. show... (AXB) . (CXD) = (A.C)(B.D) - (A.D)(B.C) here's what i have done but its partially correct. (AXB)i = \varepsilon_{ijk}A_jB_k. (CXD)i = \varepsilon_{ijk}C_jD_k so (AXB) . (CXD) =...
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    Fourier series for exponentials even or odd function?

    hi peeps. just a quick one. (a) how would you go around working out the Fourier for exponential functions.. simply something like e^x? (b) and how can this be applied to work out Fourier series for cosh and sinh (considering cosh = e^x + e^-x / 2) etc etc.. first of all.. is e^x even or...
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    Differentiability and continuity confusion

    i was attempting to cancel everything out at the end without considering obvious facts in the beginning but i guess that would be a mistake.. for the right hand limit: \lim_{h\to 0+} \frac{f(0+h)-f(0)}{h} = \lim_{h\to 0+} \frac{{\sin \frac{1}{0+h}}-f(0)}{h} = \lim_{h\to 0+} \frac{{\sin...
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    Differentiability and continuity confusion

    thnx for all the advice.. I've done some research on this and I've just still got a bit of problem here... i want to prove that sin(1/x) is not differentiable by using the LIMITS method.. [SIZE="3"]ive worked this out so far: the left hand limit and right hand limits need to be proved...
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    Vector Calculus Subscript Notation

    thanks a lot for that. it does help but there is far too much information there. i was just looking for a general explanation of the fundamentals and how the notations can be used to solve questions such as proving that: grad(A.B) = (B.Delta)A + (A.Delta)B + BX(CurlA) + AX(CurlB) etc etc...
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    Vector Calculus Subscript Notation

    Hi there is there a tutorial or post explaining vector calculus subscript notation please? e.g. Eijk Kklm dil djm etc etc is there a tutorial explaining these thoroughly and how these can convert into div grad and curl?? i've used the search engine but can't seem to find them. thnx
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    Differentiability and continuity confusion

    the function is definitely sin(1/x) and NOT x.sin(1/x) so basically am i right in assuming that to answer a question like this (show its not differentiable at 0), i have to first show that its discontinuous at 0 and deduce that since its discontinuous at 0 then it can't be differentiable at 0...
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    Differentiability and continuity confusion

    a function is differentiable if [ f(x) - f(xo) / (x - x0) ] exists i can appreciate i have to do this.. but how would i show that this derivative doesn't exist at 0... n wuld it be continuous at that point or not?but from here
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    Differentiability and continuity confusion

    Hi there just a general question: this involves continuity and differentiability suppose: f(x) = sin 1/x if x not equal to 0 f(0) = 0 PROVE F IS NOT DIFFERENTIABLE AT 0 i understand if it is not differentiable at 0 then it may not be continuous at 0. however is there...
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