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    I cant bring myself to do any c3 revision after doing bad in the jan 2013 paper
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    (Original post by QwertyG)
    I cant bring myself to do any c3 revision after doing bad in the jan 2013 paper
    Remind yourself that c3 is worse than c4 and once you've done c3 revision you can revise/do an easier paper, aka c4
    Im starting c3 on Monday
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    So how much revision does everyone plan to do over the Easter holidays?


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    Our teacher gave us this question a while back...I quite liked it.

    I thought people here may like to see it/have a go.

    \displaystyle\int e^{3x} \cos(2x) dx

    Leave answers in spoilers so that others can have a go if they want to.

    (Original post by m4ths/maths247)
    This may help:

    http://www.youtube.com/watch?v=Gf_e0KD0kZw
    I like your videos.
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    (Original post by usycool1)



    I like your videos.
    Thanks
    I am trying to get everything from C1-4, D1, M1 and S1 uploaded for complete revision before the exam.
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    (Original post by usycool1)
    Our teacher gave us this question a while back...I quite liked it.

    I thought people here may like to see it/have a go.

    \displaystyle\int e^{3x} \cos(2x) dx

    Leave answers in spoilers so that others can have a go if they want to.



    I like your videos.

    Spoiler:
    Show




    Do I need to factorise the 1/9 along with something?
    I have restarted this question like 3 times lol..

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    (Original post by usycool1)
    Our teacher gave us this question a while back...I quite liked it.

    I thought people here may like to see it/have a go.

    \displaystyle\int e^{3x} \cos(2x) dx

    Leave answers in spoilers so that others can have a go if they want to.



    I like your videos.
    My teacher gave me a question like that (but with different numbers). It took me about an hour (during my free period) to notice what I was meant to do! I got it in the end though .
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    (Original post by usycool1)
    Our teacher gave us this question a while back...I quite liked it.

    I thought people here may like to see it/have a go.

    \displaystyle\int e^{3x} \cos(2x) dx

    Leave answers in spoilers so that others can have a go if they want to.



    I like your videos.
    So I think I have the right method, but could you tell me if I have the right answer:

    Spoiler:
    Show
    I=\int e^{3x}cos(2x) dx


    u=e^{3x}, \frac{du}{dx}=3e^{3x}, \frac{dv}{dx}=cos(2x), v=\frac{1}{2}sin(2x)


    I=\frac{1}{2}e^{3x}sin(2x)-\frac{3}{2}\int e^{3x}sin(2x) dx


    J=\int e^{3x}sin(2x) dx


    u=e^{3x}, \frac{du}{dx}=3e^{3x}, \frac{dv}{dx}=sin(2x), v=-\frac{1}{2}cos(2x)


    J=\frac{-1}{2}e^{3x}cos(2x) + \frac {3}{2}\int e^{3x}cos(2x) dx


    J=\frac{-1}{2}e^{3x}cos(2x) + \frac {3}{2}I


    I=\frac{1}{2}e^{3x}sin(2x)-\frac{3}{2}(-\frac{1}{2}e^{3x}cos(2x) + \frac {3}{2}I)


    I=\frac{1}{2}e^{3x}sin(2x) + \frac{3}{4}e^{3x}cos(2x)- \frac{9}{4}I


    \frac{13}{4}I=\frac{1}{4}e^{3x}(  2sin(2x) + 3cos(2x))


    \boxed{I=\frac{1}{13}e^{3x}(2sin  (2x)+3cos(2x)) + C}
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    (Original post by brittanna)
    So I think I have the right method, but could you tell me if I have the right answer:

    Spoiler:
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    I=\int e^{3x}cos(2x) dx

    u=e^{3x}, \frac{du}{dx}=3e^{3x}, \frac{dv}{dx}=cos(2x), v=\frac{1}{2}sin(2x)

    I=\frac{1}{2}e^{3x}sin(2x)-\frac{3}{2}\int e^{3x}sin(2x) dx

    J=\int e^{3x}sin(2x) dx

    u=e^{3x}, \frac{du}{dx}=3e^{3x}, \frac{dv}{dx}=sin(2x), v=\frac{-1}{2}cos(2x)

    J=\frac{-1}{2}e^{3x}cos(2x) + \frac {3}{2}\int e^{3x}cos(2x) dx

    J=\frac{-1}{2}e^{3x}cos(2x) + \frac {3}{2}I

    I=\frac{1}{2}e^{3x}sin(2x)-\frac{3}{2}(\frac{-1}{2}e^{3x}cos(2x) + \frac {3}{2}I)

    I=\frac{1}{2}e^{3x}sin(2x) + \frac{3}{4}e^{3x}cos(2x)- \frac{9}{4}I

    \frac{13}{4}I=\frac{1}{4}e^{3x}(  2sin(2x) + 3cos(2x))

    I=\frac{1}{13}e^{3x}(2sin(2x)+3c  os(2x))
    Spoiler:
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    Correct!

    Just one thing though...you don't need two seperate variables (I and J), you can just one.


    (Original post by QwertyG)
    Spoiler:
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    Do I need to factorise the 1/9 along with something?
    I have restarted this question like 3 times lol..

    Spoiler:
    Show

    You should have:

    \displaystyle\int e^{3x} cos 2x \ dx = \dfrac{1}{3}e^{3x} \cos 2x + \dfrac{2}{9}e^{3x} \sin 2x - \dfrac{4}{9} \displaystyle\int e^{3x} \cos 2x \ dx

    (you've probably omitted the first part accidentally or something).

    Now let I = \displaystyle\int e^{3x} cos 2x \ dx and see if that helps.
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    (Original post by usycool1)
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    Correct!

    Just one thing though...you don't need two seperate variables (I and J), you can just one.




    Spoiler:
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    You should have:

    \displaystyle\int e^{3x} cos 2x \ dx = \dfrac{1}{3}e^{3x} \cos 2x + \dfrac{2}{9}e^{3x} \sin 2x - \dfrac{4}{9} \displaystyle\int e^{3x} \cos 2x \ dx

    (you've probably omitted the first part accidentally or something).

    Now let I = \displaystyle\int e^{3x} cos 2x \ dx and see if that helps.
    I know, I just usually end up missing a negative sign or something when I don't .
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    (Original post by usycool1)
    ...

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    I did it thanks for correcting mistake

    although in the exam me being me wouldnt simplify the answer would examiners accept this?




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    (Original post by QwertyG)
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    I did it thanks for correcting mistake

    although in the exam me being me wouldnt simplify the answer would examiners accept this?




    That would be fine .
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    (Original post by brittanna)
    That would be fine .
    Have you finished learning the whole of c4?
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    (Original post by QwertyG)
    Have you finished learning the whole of c4?
    Yeah, we finished it a couple of lessons ago. How far through it are you?
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    (Original post by QwertyG)
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    I did it thanks for correcting mistake

    although in the exam me being me wouldnt simplify the answer would examiners accept this?




    Hmm...would a question like that ever come up in an exam? :holmes: If so, how many marks do you think it'd be?
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    (Original post by brittanna)
    Yeah, we finished it a couple of lessons ago. How far through it are you?
    Just got vectors left. How did long did it take you to learn vectors? I been avoiding it for quite some time now I gotta learn it
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    (Original post by QwertyG)
    Just got vectors left. How did long did it take you to learn vectors? I been avoiding it for quite some time now I gotta learn it
    I guess it took us about four lessons. Our teacher just made a booklet with the different types of questions they can ask and we worked through those for our teaching of the vectors chapter. There isn't really that much in it (although I still don't like them).
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    (Original post by brittanna)
    t made a booklet with the different types of questions they can as

    I guess it took us about four lessons. Our teacher just made a booklet with the different types of questions they can ask and we worked through those for our teaching of the vectors chapter. There isn't really that much in it (although I still don't like them).
    Were they textbook questions or past paper questions in the booket? so you started past/solomon papers ?
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    (Original post by usycool1)
    Hmm...would a question like that ever come up in an exam? :holmes: If so, how many marks do you think it'd be?
    lol i hope it comes up in the exam so I would actually know how do it. I dont know how many marks though it took me sometime getting the final answer despite making a mistake at the start :X
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    (Original post by QwertyG)
    Were they textbook questions or past paper questions in the booket? so you started past/solomon papers ?
    I'm not sure. I'm guessing textbook or made up as some of the first ones were really basic (to introduce us to it) and I can't imagine they would have come up in an exam. I've done one past paper and one solomon paper. Although I still need to look over the factor formulae (trigonometry) as I didn't do them properly in C3 and you need them to integrate some things.
 
 
 
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