• gbzm@lemmy.world
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    4 months ago

    You have no idea. This is tame compared to some of the shit I seen in my masters.

    I remember one time we had an exercise where the calculation yielded a violently nonconvergent improper integral.

    Now, we had already been introduced to some “tricks” to “deal with” those. And I do mean “tricks” as in magic. Arcane spells best described as “praying to the obscure gods of Borel summation until some incantation accidentally summoned untold horrors that would swallow infinities into fractional dimensions converging to zero” or some bullshit like that.

    But this one was so bizarre that the whole class was stumped. Our runes were powerless, what remained of our sanities was fraying and disappearing into the abyss that kept lookingback for more.

    Then the TA just tsk’d at our collective weakness, deadass looked into each of our eyeballs and wrote this on the blackboard

    I almost puked on the spot

  • Borger@lemmy.blahaj.zone
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    5 months ago

    If anyone’s curious, the first step is wrong. e^x minus its integral is a constant. Not necessarily zero.

    • Kogasa@programming.dev
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      5 months ago

      Ok. Take the derivative of both sides and integrate at the end, then plug in a value of x to get C = 0.

  • pankuleczkapl@lemmy.dbzer0.com
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    5 months ago

    Except the first assumption that e^x = its own integral, everything else actually makes sense (except the DX are in the wrong powers). You simply treat the “1” and “integral dx” as operators, formally functions from R^R into R^R and “(0)” as calculating the value of the operator on a constant-valued function 0. EDIT: the step 1/(1-integral) = the limit of a certain series is slightly dubious, but I believe it can be formally proven as well. EDIT 2: I was proven wrong, read the comments

      • Alteon@lemmy.world
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        5 months ago

        I don’t believe you can just factor our e^x in the second step like that. That seems in incorrect to me. Then again I’ve been out of calculus for years now.

        • Fermion@feddit.nl
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          5 months ago

          The process is horribly wrong, but the answer is correct. I think that’s the intended joke.