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Weird double integral. Please help

  1. Jun 7, 2012 #1
    Weird double integral. Please help!!

    its from thermodynamics...but i dont think you really need to understand thermodynamics to figure out what math trick they used to get from the first integral to the second integral
    http://img833.imageshack.us/img833/833/intek.png [Broken]


    i have been looking at this equation for hours and cannotfigure out how that partial differential and the 'dT' just disappeared!!
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Jun 7, 2012 #2

    chiro

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    Re: Weird double integral. Please help!!

    Hey racnna and welcome to the forums.

    Are you familiar with identities involving the fundamental theorem of calculus?
     
  4. Jun 7, 2012 #3
    Re: Weird double integral. Please help!!

    hey chiro...no im not..or maybe i have just forgotten....i just googled but cant seem to find any useful info....can you please explain this identity or link me to a place that explains it? thanks!
     
  5. Jun 7, 2012 #4
    Re: Weird double integral. Please help!!

    they evaluated the dt integral using the fact that [itex]\int_a^b \partial _x f(x,y) dx = f(b,y)-f(a,y)[/itex]

    you might find this helpful;
    http://en.wikipedia.org/wiki/Differentiation_under_the_integral_sign
     
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