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    P = (2800ae^0.2t)/(1+ae^0.2t)

    a=0.12

    Show that p = 336/(0.12+e^-0.2t)

    I get that if you divide by e^0.2t you get the answer, but why do you do this ?

    Help much apprieciated, thanks in advance
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    (Original post by style)
    P = (2800ae^0.2t)/(1+ae^0.2t)

    a=0.12

    Show that p = 336/(0.12+e^-0.2t)

    I get that if you divide by e^0.2t you get the answer, but why do you do this ?

    Help much apprieciated, thanks in advance
    Are you asking what the point of the question is? Like, why do they want to express p in that form? Without more context, there doesn't seem to be any sensible reason.
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    I don't understand what you mean You already know what to do, divide through by e^0.2t. The reason you do it is to get the mark...
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    I think the question is whether you're able to apply it so something else after solving it. Obviously not whether you get a mark or not for doing the right thing.
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    P = \dfrac{2800ae^{0.2t}}{1+ae^{0.2t  }}

    P = \dfrac{2800a}{\frac{1}{e^{0.2t}+  a}}

    P = \dfrac{2800a}{\frac{1}{e^{0.2t}+  a}}

    P = \dfrac{2800\times0.12}{e^{-0.2t}+0.12}

    P = \dfrac{336}{e^{-0.2t}+0.12}
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    (Original post by JoshFlack)
    I don't understand what you mean You already know what to do, divide through by e^0.2t. The reason you do it is to get the mark...
    It's because thats what I did before a few months ago when I did this question, re doing it now I don't remember the reasoning behind it.
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    (Original post by Swayum)
    Are you asking what the point of the question is? Like, why do they want to express p in that form? Without more context, there doesn't seem to be any sensible reason.
    No, I was stuck on this question but looking over some previous notes i saw that I divided it by e^0.2t to get the answer. But the thing is I don't remember why I did that, and I can't figure out the reasoning behind it.
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    (Original post by style)
    No, I was stuck on this question but looking over some previous notes i saw that I divided it by e^0.2t to get the answer. But the thing is I don't remember why I did that, and I can't figure out the reasoning behind it.
    if i remember correctly, part of the question was just getting you to rearrange it. you know like how they do that in numerical methods questions
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    Just forget it, its only worth 1 mark.
    Thanks every1
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    (Original post by maxfire)
    P = \dfrac{2800ae^{0.2t}}{1+ae^{0.2t  }}

    P = \dfrac{2800a}{\frac{1}{e^{0.2t}+  a}}

    P = \dfrac{2800a}{\frac{1}{e^{0.2t}+  a}}

    P = \dfrac{2800\times0.12}{e^{-0.2t}+0.12}

    P = \dfrac{336}{e^{-0.2t}+0.12}
    could you explain the second step please, thanks.
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    (Original post by skk90)
    could you explain the second step please, thanks.
    Divide the top and the bottom of the fraction by e^{0.2t}
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    P=(336e^0.2t)/(1+0.12e^0.2t)
    then factorise out e^0.2t on the bottom, giving you ((1/e^0.2t)+0.12) you can then cancel out e^02t
    then the 1/e^0.2t gives you the e^-0.2t
    therefore giving you the answer
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    (Original post by maxfire)
    Divide the top and the bottom of the fraction by e^{0.2t}
    How did u divide the bottom part of the fraction by it?
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    e^0.2t(1/e^0.2t)+0.12)
    you get that
    then (1/e^0.2t)+0.12=0.12+e^-0.2t
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    How do I differentiate y= cot x^2 (not cot^2 x)
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    (Original post by skk90)
    How do I differentiate y= cot x^2 (not cot^2 x)
    Use the chain rule: the derivative of f(g(x)) is g'(x) f '(g(x)).

    [The derivative of cot x is -cosec^2 x].
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    (Original post by meatball893)
    Use the chain rule: the derivative of f(g(x)) is g'(x) f '(g(x)).

    [The derivative of cot x is -cosec^2 x].
    Why isn't the g'(x) multiplied by f ?
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    (Original post by skk90)
    How do I differentiate y= cot x^2 (not cot^2 x)
    in order to differentiate cotf(x) you use: -f'(x)cosec2f(x)

    therefore, the answer would be: -2xcosex2x2
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    (Original post by skk90)
    How do I differentiate y= cot x^2 (not cot^2 x)
    if im not wrong its: -2cotxcosec^2.x using the chain rule on (cotx)^2 leting u=cotx and y=u^2
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    (Original post by amzy2)
    if im not wrong its: -2cotxcosec^2.x
    how come? I'm pretty sure it's -2xcosec2x2.
 
 
 
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