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Math Help - Natural log problem

  1. #1
    Newbie
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    Natural log problem

    I am doing a flight control module at university, and maths has never been a strong point of mine.

    My problem is:

    y(t)=k(1-e^-t/T)

    Where y(t)=0.5, k=6/17 and T=1/17

    So i can get to this point:

    (0.5)17/6 = 1-e^-17t

    But obviously if i go any further i am going to have to take natural log of a negative number which obviously cannot be done and i dont know anyway around it.

    Any help would be great

    Thanks
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  2. #2
    MHF Contributor
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    The supremum of 1 - e^(-t/T) is 1 (see this graph, which approaches 1 very fast because of the large factor of 17). So, the supremum of y(t) is 6/17 < 0.5, which means that there are no solutions.
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