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AQA Core 4 - Monday 10th June 2013 (AM) - Official Thread Watch

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    I may seem stupid asking this, but what was the way to do question 1 part c? I'm not thick, I just wasn't seeing it
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    (Original post by chocolate102030)
    can someone explain the by parts question to me thanks

    (Original post by Newtonsfirsthore)
    Can someone please explain how you get 3.65 for question 8? I keep on getting 3.43 when I put t=45 into the answer of unofficial mark scheme
    a)  \int t cos(\frac{\pi}{4}t) dt

    u = t \Rightarrow u'=1

    v' = cos(\frac{\pi}{4}t) \Rightarrow v = \frac{4}{\pi}sin(\frac{\pi}{4}t)

    \int = uv - \int vu' dt= \frac{4}{\pi}tsin(\frac{\pi}{4}t  ) - \int \frac{4}{\pi}sin(\frac{\pi}{4}t) dt+c

     \frac{4}{\pi}tsin(\frac{\pi}{4}t  ) + \frac{16}{\pi^2}cos(\frac{\pi}{4  }t)+c



    b) \frac{dx}{dt}= \frac{t cos(\frac{\pi}{4}t)}{32x}

    \int x dx = \frac{1}{32} \int  t cos(\frac{\pi}{4}t) dt

    \frac{x^2}{2} = \frac{1}{32}[\frac{4}{\pi}tsin(\frac{\pi}{4}t  ) + \frac{16}{\pi^2}cos(\frac{\pi}{4  }t)+c]

    \frac{x^2}{2} = \frac{1}{8\pi}tsin(\frac{\pi}{4}  t) + \frac{1}{2\pi^2}cos(\frac{\pi}{4  }t)+c

    Sub in x = 4 and t = 0;

    8 = \frac{1}{2\pi^2} + c \Rightarrow c = 8 - \frac{1}{2\pi^2}

    So:

    \frac{x^2}{2} = \frac{1}{8\pi}tsin(\frac{\pi}{4}  t) + \frac{1}{2\pi^2}cos(\frac{\pi}{4  }t)+8 - \frac{1}{2\pi^2}

    When t = 45 (type it into your calculator carefully);

    \frac{x^2}{2} = 6.647

    x^2=13.295

    x = 3.646 \Rightarrow x = 3.65m or 365cm to the nearest cm
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    (Original post by SqueakyMoose)
    I may seem stupid asking this, but what was the way to do question 1 part c? I'm not thick, I just wasn't seeing it
    From the part just before it, did you get C = 2?
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    (Original post by mulac1)
    I'm trying to add together all the marks but its coming to a total of 72
    this is what I get each question out of:
    1) /10
    2) /8
    3) /7
    4) /11
    5) /9
    6) /14
    7) /3
    8) /10
    BUMP - anyone got any idea about this?
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    (Original post by Jamie T)
    Anyone have physics on Thursday?
    Aye
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    Could someone show me how to do the vector question please? much appreciated
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    (Original post by fizzbizz)
    x
    According to this I've more than likely got what I need for my A overall. It was a pretty big long shot for me to get an A* anyway so I'm not to bothered. On to the next exam!
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    (Original post by fizzbizz)
    From the part just before it, did you get C = 2?
    what was question 1c?
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    (Original post by SqueakyMoose)
    I may seem stupid asking this, but what was the way to do question 1 part c? I'm not thick, I just wasn't seeing it
    It was quite sly
    You had to divide the expression because it was improper, then you end up with 2 + the partial fraction equation from part A, then you just integrate as normal but stick a 2x in there
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    I tell myself after every exam I wont end up on the student room to check my answers.. But yeah this was solid and hated every second of it.. Saying goodbye to my A* I'm thinking..
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    (Original post by Bumble333)
    Can anyone remember the bionimial ?
    (1+6x)^-1/3
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    **** that. Handing my CV into McDonalds tomorrow. Goodbye university. Goodbye all hopes of a nice life. All because there is one **** of an examiner out there probably cackling with glee right now.
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    Actually, I made some stupid mistakes on the parametric equations. I think at worst case scenario (no marks for working out) that's 65/75. And yeah, I need 83 UMS.

    If I was to predict the boundaries;

    100 - 67
    90 - 61
    80 - 55

    Sounds about right??
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    (Original post by Prepotency)
    Actually, I made some stupid mistakes on the parametric equations. I think at worst case scenario (no marks for working out) that's 65/75. And yeah, I need 83 UMS.

    If I was to predict the boundaries;

    100 - 67
    90 - 61
    80 - 55

    Sounds about right??
    Yeah sounds right to me! Maybe +1 to each one
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    (Original post by Prepotency)
    Actually, I made some stupid mistakes on the parametric equations. I think at worst case scenario (no marks for working out) that's 65/75. And yeah, I need 83 UMS.

    If I was to predict the boundaries;

    100 - 67
    90 - 61
    80 - 55

    Sounds about right??
    Seems legit.
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    (Original post by fizzbizz)
    From the part just before it, did you get C = 2?
    I did. Though I can't really remember why or how, was kinda a last minute rush sort of thing :P

    and then for the part below it was like:
    2x + whatever the ln answer was.
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    (Original post by Prepotency)
    Actually, I made some stupid mistakes on the parametric equations. I think at worst case scenario (no marks for working out) that's 65/75. And yeah, I need 83 UMS.

    If I was to predict the boundaries;

    100 - 67
    90 - 61
    80 - 55

    Sounds about right??
    I think I'm about the same as you, with a worse case dropping about 10 (should be less, but you never know). I need 92 for an A* so it is definitely possible. Still, was a tough exam.
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    how many marks will i lose in the differential equation question, if instead of doing 1/(pi/4) = 4/pi i did 1/(pi/4) = 4pi hence got all the subsequent working and answer wrong? anyone know?
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    i can't remember what question 1 is, can someone remind me please? im kind of freaking out now cuz i can't remember if i have got anything like 11/3 ln2!:bawling:
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    (Original post by Bord3r)
    I think I'm about the same as you, with a worse case dropping about 10 (should be less, but you never know). I need 92 for an A* so it is definitely possible. Still, was a tough exam.
    Can you remember how many marks the 'find the co-ordinate where the line crosses the x-axis' in the parametric question? I think I wrote x=2, instead of x=-2, so the next part was wrong (I did the method right though).

    This is where I lost my marks;

    - Last part of the Vector Question. I just found length AC and wrote A=1/2absin(c). I'll probably lose all 4 marks though.

    - I couldn't find the k value in the dh/dt thing, so that will be 1 or 2 marks lost.

    - Then the silly mistakes in the parametric question have probably cost me 4 marks maximum.
 
 
 
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