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AQA Core 3 - Thursday 6th June 2013 (AM) - Official Thread Watch

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    For the last question the working is:

    u=x^1/2
    Integral = (1/x^1/2) X 1/(1+x^1/2)
    du/dx= 1/2x^1/2
    2du/dx=1/x^1/2
    Integral =(1/1+u) X 2du/dx
    limits are now 2 and 1
    Integral = 2/1+u
    = 2ln(1+u)
    answer= 2ln(3)-2ln(2) =2ln(3/2)
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    (Original post by edina101morris)
    hang on, i think y=(2x-3)

    then think f-1(x) was (e^x+3)/2

    not sure cant quite remeber :confused:
    I knew there was a 3 somewhere I couldn't remember, I think you are right might have put that as well.
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    (Original post by stuart_aitken)
    Ummmmm. I didn't draw it. My graph software did!

    There's the logic/

    y = pi - cos^-1(x)
    It's define for -1<x<1, because cos# cannot be outside this range. Therefore the limits for x are -1 to +1. So for the important values:

    x= -1
    y = pi - cos^-1(-1) = pi - pi = 0
    (-1,0)>>>end point

    x = 0
    y = pi - cos^-1(0) = pi - pi/2) = pi/2
    (0,pi/2)>>>y-intercep
    x = 1,
    y = pi-cos^1(1) = pi - 0 = pi
    (1,pi)>>>end point

    As can be seen from these results, the graph I drew is surely correct :confused:
    Sorry you are right
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    (Original post by sophonax1)
    For the last question the working is:

    u=x^1/2
    Integral = (1/x^1/2) X 1/(1+x^1/2)
    du/dx= 1/2x^1/2
    2du/dx=1/x^1/2
    Integral =(1/1+u) X 2du/dx
    limits are now 2 and 1
    Integral = 2/1+u
    = 2ln(1+u)
    answer= 2ln(3)-2ln(2) =2ln(3/2)
    Yay! But tbh, I'm not worried about integrals as I just checked em on my calculator.
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    [QUOTE=Samtaylor47;43004668]
    (Original post by Dinomouse)
    I got 160pi/3 for the vase question and 5.05 and 1.23 for the 7 mark question with sec squared in.

    For the volume question, I got the answer as 73/3 pi and checked in my calculator and it was the same?
    This question was one i was fairly sure with haha. I don't know how you got the same answer with 73/3 pi, maybe a typing into calculator mistake?
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    (Original post by ryanc_95)
    for the last one i got 2ln2+2. A few people have also said they got this, is this correct or is it 2ln(3/2)?
    I got this!!!


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    What do you think method marks will be like on the last question?
    I managed to work out that 2du = 1/X^0.5 dx but then when it came to integrating it did it all wrong :/
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    Okay so aqa have shown us how much they like graphs this year.
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    I just rearranged the whole equation to find x^2 and then integrated it?
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    (Original post by Dirtybit)
    Okay so aqa have shown us how much they like graphs this year.
    they went a little overboard...
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    For inequalities did u guys get x less than or equal to one and then x is greater than or equal to one ?
    And for the question on the intercepts about ln bla bla the 2nd last part where it says find fg(x) in a certain form, anyone remember the answer?
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    For the last question I did everything right but put du/dx instead of dx/du I then followed all this through and got a very complicated answer. How many (out of 7) marks would I get?
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    Think it will be about 70 for 90ums and 64 for 80ums. What does everyone else think? I need an A* and I think I've dropped about 10 marks.
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    One of the many questions that confused me was the secx 5 one I only got two answers and that seems wrong for a 7 mark question... can any one clarify please
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    (Original post by esen212)
    One of the many questions that confused me was the secx 5 one I only got two answers and that seems wrong for a 7 mark question... can any one clarify please
    I got that too. You had to discard one of the values and the remaining value yielded 2 x solutions.
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    (Original post by Dirtybit)
    For inequalities did u guys get x less than or equal to one and then x is greater than or equal to one ?
    And for the question on the intercepts about ln bla bla the 2nd last part where it says find fg(x) in a certain form, anyone remember the answer?
    I got x<=1 and x>=3. For the fg(x) part, I don't remember too well but ln8/2??
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    Guys what was the first integration question on the last page?
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    (Original post by esen212)
    One of the many questions that confused me was the secx 5 one I only got two answers and that seems wrong for a 7 mark question... can any one clarify please
    I got the same, cant have cos-1 of -3.
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    (Original post by esen212)
    One of the many questions that confused me was the secx 5 one I only got two answers and that seems wrong for a 7 mark question... can any one clarify please
    I got 2, there were to values for cosx but one had no solutions, I think?? Answer was 5.05 and 1.??
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    Came out thinking it was just about OK. Then discussed with friends and now I'm worried. Definitely got the final answers to the vase question and last integration by substitution question wrong. And there were many question where we had to draw graphs. Not sure if they were right either...

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