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    (Original post by Doughboy)



    Also, how the flap do you find P?
    What paper is that question from?
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    Starting on the past papers today until wednesday. Fun times.
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    (Original post by ArchedEdge)
    What paper is that question from?
    Edexcel Jun 2008 C3
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    Not long now :| I've done every past paper at least twice.


    What to doooooooooo?
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    (Original post by Get Cape.Wear Cape.Fly.)
    Not long now :| I've done every past paper at least twice.


    What to doooooooooo?
    Do it again? To make sure you know how to do EVERY SINGLE question. If you know how to do that then do the practice papers. If you done that then do the elmwood papers. If you done that do the solomon papers. And make sure you know how to all the questions. And if you done that (lol) do all the questions from the text book. ANd if you done that...well...you're guaranteed to get 100% . :woo:
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    (Original post by Superman_Jr)
    Do it again? To make sure you know how to do EVERY SINGLE question. If you know how to do that then do the practice papers. If you done that then do the elmwood papers. If you done that do the solomon papers. And make sure you know how to all the questions. And if you done that (lol) do all the questions from the text book. ANd if you done that...well...you're guaranteed to get 100% . :woo:
    I think your username is really hot.
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    (Original post by LysiaK)
    The trig identity for cos(A) - cos(B) is in the formula booklet: -2sin(\frac{A+B}{2})sin(\frac{A-B}{2}).


    If you meant you wanted the proof:

    Use the identities
    cos(A + B) = cos(A)cos(B) - sin(A)sin(B)
    and
    cos(A - B) = cos(A)cos(B) + sin(A)sin(B)

    Subtract one from the other
    cos(A + B) - cos(A - B) = -2sin(A)sin(B)

    Let A + B = P and A - B = Q
    so, A = \frac{P + Q}{2} and B = \frac{P - Q}{2}

    Therefore, cos(P) + cos(Q) = -2sin(\frac{P + Q}{2})sin(\frac{P - Q}{2})

    And in your case, you'd just sub in the 5x and x as P and Q
    Can anybody else confirm that this has been taken out of this syllabus?
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    (Original post by sb1234)
    Can anybody else confirm that this has been taken out of this syllabus?
    lol since when was it in the syllabus :shifty:
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    (Original post by Get Cape.Wear Cape.Fly.)
    I think your username is really hot.
    Are you hitting on me? :eek: Because I like!
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    (Original post by sb1234)
    Can anybody else confirm that this has been taken out of this syllabus?
    I don't think so. If it's in the formula sheet and in the book it must be in the specification
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    (Original post by Superman_Jr)
    Are you hitting on me? :eek: Because I like!
    :hubba:
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    (Original post by Superman_Jr)
    I don't think so. If it's in the formula sheet and in the book it must be in the specification
    It's in the book?!! Nooooooooooooooooooooooooooooooo oooooooooo! K, back to revision then.
    • PS Helper
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    PS Helper
    (Original post by sb1234)
    Can anybody else confirm that this has been taken out of this syllabus?
    it is in the syllabus
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    guyssss
    someone tell me what this is, cuz i'm sure i did it right but the mark scheme says something else.

    4cosx + 6sinx in the form Rsin(x+z)

    Sooooo, 4^2 + 6^2 rooted is 52 sqrt

    then Rsinz = 6 and Rcosz = 4

    tanz = 6/4 = 56.8

    is this righttt?
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    What does the mark scheme say?
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    (Original post by jaz_jaz)
    guyssss
    someone tell me what this is, cuz i'm sure i did it right but the mark scheme says something else.

    4cosx + 6sinx in the form Rsin(x+z)

    Sooooo, 4^2 + 6^2 rooted is 52 sqrt

    then Rsinz = 6 and Rcosz = 4

    tanz = 6/4 = 56.8

    is this righttt?
    Rsin(x+z)= Rsinxcosz + Rcosxsinz = 4cosx + 6sinx

    comparing the coefficients of cosx and sinx,

    sinx: Rcosz = 6

    cosx: Rsinz = 4

    So I think thats where you went wrong.
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    (Original post by samir12)
    Rsin(x+z)= Rsinxcosz + Rcosxsinz = 4cosx + 6sinx

    comparing the coefficients of cosx and sinx,

    sinx: Rcosz = 6

    cosx: Rsinz = 4

    So I think thats where you went wrong.
    Ohh I see thanks.
    I can't do the next bit and its driving me insane!
    Help :angel:
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    Generally how high are the grade boundaries for C3 ? I'm just about scraping an A (60 Marks) with the past papers I'm doing, I'm scared it might do me over in the real exam if the grade boundaries are particularly high.
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    (Original post by jaz_jaz)
    Ohh I see thanks.
    I can't do the next bit and its driving me insane!
    Help :angel:
    What next bit, working out z? Same thing as you done in your working only it will be tanz= 4/6
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    Can I ask a question about RCos RSin

    If there is something like 3Sinx + 2Cosx - how do you work out A and B because in this RCosx=3 but thats the Sin coefficient originally not the cos one.

    Bad wording I know :P
 
 
 
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