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    (Original post by TeeEm)
    http://www.thestudentroom.co.uk/show....php?t=3327325

    look at post 244, PDF 9/10 for similar types
    those questions are crazy, if you wrote the c4 paper boundaries would hit 30 for a
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    (Original post by Dante991)
    I did really well in the June 14 paper, but I really dont understand this question?? Can someone help me on it
    part b~?
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    Both haha, just baffled by this but otherwise really nice paper

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    (Original post by studentwiz)
    those questions are crazy, if you wrote the c4 paper boundaries would hit 30 for a
    I cater mainly for mathematicians to be, that is true, but I am still inclusive.
    My resources have huge range, but is is true I have a lot of very hard stuff.
    Stick to mainstream.
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    (Original post by TeeEm)
    question made.
    Had a stab at the one you posted before just now - had to go for dinner. Haven't looked at answer so hints would be appreciated. I remember seeing a video on khan academy once where he did this 'disc' method. At the moment I'm trying to find a somewhat general equation for the volume of a disc with the hope that i can sum the volumes of these discs using integration. I'm struggling to give a general height to the discs if that makes sense.Can i call it dy - as in 'small change in y'?
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    HELP WITH SCALAR PRODUCT RULE

    If it asks for angle ACB do I use direction vectors of AC and BC to work it out, or of AC and CB?
    In June 2014 the proof was using the first option, whereas June 2014 replacement seems the be the second option as I got the wrong answer the other way :'(
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    how to integrate sin3xcos2x?? using identities in c3 formula booklet

    apparently sin3xcos2x=0.5(sin5x + cos3x)

    but I don't understand how
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    (Original post by ThoughtIsFree)
    how to integrate sin3xcos2x?? using identities in c3 formula booklet

    apparently sin3xcos2x=0.5(sin5x + cos3x)

    but I don't understand how
    Use factor formulae - they're given in the booklet.
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    (Original post by usycool1)
    Use factor formulae - they're given in the booklet.
    ive tried but I cant do it
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    (Original post by Gilo98)
    Had a stab at the one you posted before just now - had to go for dinner. Haven't looked at answer so hints would be appreciated. I remember seeing a video on khan academy once where he did this 'disc' method. At the moment I'm trying to find a somewhat general equation for the volume of a disc with the hope that i can sum the volumes of these discs using integration. I'm struggling to give a general height to the discs if that makes sense.Can i call it dy - as in 'small change in y'?
    I supplied solution look at it...
    Failure to do this translate the curve left by 4 units, and revolve about the y axis.

    I made a question according to the 3 specs now.
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    (Original post by TeeEm)
    I cater mainly for mathematicians to be, that is true, but I am still inclusive.
    My resources have huge range, but is is true I have a lot of very hard stuff.
    Stick to mainstream.
    Just out of curiosity would you say the papers other than s and t are equal difficulty to the normal papers or are they harder?


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    (Original post by TeeEm)
    I supplied solution look at it...
    Failure to do this translate the curve left by 4 units, and revolve about the y axis.

    I made a question according to the 3 specs now.
    tsr phone app is being awkward - i wanted to post pic of my method but got the answer - turns out i basically did it exactly how the solution did it only i did the dy/dt dt substitution bit earlier, at first sight of dy. Will have a go at the other one now - where can i find it?
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    (Original post by Medicjug)
    Just out of curiosity would you say the papers other than s and t are equal difficulty to the normal papers or are they harder?


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    On average they are far harder.
    (I am sure you can form your own opinion)
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    (Original post by Gilo98)
    tsr phone app is being awkward - i wanted to post pic of my method but got the answer - turns out i basically did it exactly how the solution did it only i did the dy/dt dt substitution bit earlier, at first sight of dy. Will have a go at the other one now - where can i find it?
    what other one?
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    (Original post by TeeEm)
    On average they are far harder.
    (I am sure you can form your own opinion)
    I did all of them for c3 apart from the two you told me to leave out and a couple of questions from s. I must say they were so helpful really helped build my confidence in tougher questions. Thank you they are very helpful.


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    (Original post by TeeEm)
    what other one?
    volume about y axis - curve given parametrically. You said you would make one and later quoted me telling me you had made it.
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    How would you guys do this

    ∫ 2 sin 3x sin 2x dx.... I dont know how to use the formula in the formula booklet for this. Pls help
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    (Original post by Gilo98)
    volume about y axis - curve given parametrically. You said you would make one and later quoted me telling me you had made it.
    I will upload it... do you want the solution too?
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    (Original post by TeeEm)
    no worries
    By the way, does stuff on graphs of secant and all that come on C4? (I know it is a C3 topic but just in case) Not too strong on it.
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    (Original post by Dante991)
    I did really well in the June 14 paper, but I really dont understand this question?? Can someone help me on it
    ok first part add them together use the additional formula for cos
    x+y=4cos(t+pi/6)+2sint
    if you expand the left hand side using the cos addition you'll see at the end -2sint cancels with 2sint and you're left with x+y=2root3cost

    part b)
    first thing you notice is they squared one side, so you have to square the other
    so squaring 2root3cost =12cost^2 and they ask for a formula that has no trig, so using the identity sin^2t+cos^t=1 rearrange to get cos^2t and from using the equation y/2=sint replace it into your equation
    so you get 12(1-y^2/4) expand and that's your answer
 
 
 
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