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    DI/DT=-16(0.5)^t(ln(0.5))
    Sub in t=3
    So it becomes -2ln0.5
    Which is the same as ln(0.5^-2)
    Which is equal to ln4


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    With integration am i right in thinking that the integral of ( k f'(x) ) / f(x) = K ln(f(x))

    So the integral 6x2 / X3+5 = 2ln(x3+5)
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    (Original post by raypalmer)
    DI/DT=-16(0.5)^t(ln(0.5))
    Sub in t=3
    So it becomes -2ln0.5
    Which is the same as ln(0.5^-2)
    Which is equal to ln4


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    I'm currently stuck on this question too!!
    Can you please explain to me what you have done?
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    (Original post by Alice Moody)
    oh....sorry thought the first bit was saying about using a substitute

    sorry
    it's fine how would you integrate that?
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    (Original post by raypalmer)
    DI/DT=-16(0.5)^t(ln(0.5))
    Sub in t=3
    So it becomes -2ln0.5
    Which is the same as ln(0.5^-2)
    Which is equal to ln4


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    thanks!
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    (Original post by manlikem)
    it's fine how would you integrate that?
    Whats the equation again?
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    (Original post by frozo123)
    thanks!
    No worries


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    (Original post by manlikem)
    what do you mean? The question is just integrate sinx cos^3 x dx
    Im tempted to say by parts?
    i will have a go on paper and let ya know
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    (Original post by Alice Moody)
    I'm currently stuck on this question too!!
    Can you please explain to me what you have done?
    First differentiate, differentiating a^x gives u a^xlna, then sub in t


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    (Original post by tiny hobbit)
    Have you done the R papers for June 2013 and June 2014? Or the C4 questions from the IAL C34 papers? They're written by the same team as write the ordinary ones.
    ah no not yet, I've encountered some questions from June 2014 R and 2013R and some from IAL in the gold papers but I haven't gone through an actual replacement paper or a IAL paper yet... I've just done the 3rd gold paper and am planning to finish the 4th one... I will probably have time for one more paper on top of that... which one do you recommend from here? thanks
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    (Original post by raypalmer)
    First differentiate, differentiating a^x gives u a^xlna, then sub in t


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    EDIT: Nevermind, sorted it!
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    (Original post by Alice Moody)
    Whats the equation again?
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    (Original post by raypalmer)
    First differentiate, differentiating a^x gives u a^xlna, then sub in t


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    OOOOOHHHHH!!!!!!!!!!!! is that c2 log laws at first?
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    (Original post by manlikem)
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    Ill have a go and get back to ya
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    (Original post by Leking9)
    For real!
    I hate consecutive exams... especially when it's 2 of my most important ones... (applying for econ at uni)....

    If only there was a day in between, or even if the econ unit 3 was in AM rather than PM...
    Ah well... what's done is done.... I dont think I'm getting that A*...
    time to just focus on C4 and then beg the maths Gods to make it low enough for me to get an A in C3...
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    When finding the shortest distance from the point to a line, how can you assume that a right angle is made between the point and the line?
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    (Original post by joe1545)
    Slightly reassuring the the last paper I've just done before I do the real thing was the Jan 2014 paper, and managed to get 98UMS.. If only tomorrow goes that well.
    Nice! don't you mean June 2014? I don't think theres a Jan 2014...
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    (Original post by Alice Moody)
    OOOOOHHHHH!!!!!!!!!!!! is that c2 log laws at first?
    If y(x) = a^x, then \log(y) = x\log(a); thus by implicit differentiation: \dfrac{1}{y}\dfrac{dy}{dx} = \log(a) \implies \dfrac{dy}{dx} = y\log(a) \implies \boxed{\dfrac{dy}{dx} = a^x\log(a)}
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    (Original post by arsenalfc97)
    When finding the shortest distance from the point to a line, how can you assume that a right angle is made between the point and the line?
    I got an idea for you
    stand 2m away from your wall
    step 1
    Walk forward ( perpendicular ) until your hand bangs against the wall

    after that
    Stand in the exact same spot, but try touching the wall at the end of the room

    which one took less less time and distance?
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    (Original post by Bustamove)
    How good are the gold papers in preparation for C4? I've done 2 today and plan to finish the other 2 by the end of today.... I've done all the papers from jan 2009 - june 14.... anyone got anymore suggestions to what other papers I should look at?
    I probably have time for one more paper along with the 2 last gold papers that I'm planning to do.. wanna get a good sleep before tomorrow to reduce my chances of making stupid mistakes...
    Can you please explain how to do part b to me? ANd hwo do you get that x = 0.1?
    https://a086a5a2f39bda93734c56a63fab...%20Edexcel.pdf
    number 4
 
 
 
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