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    Hi !
    I'm struggling with the questions on some FP1 work I got as we haven't covered any of this in class. I've worked out how to do it all apart from this question:

    Express in terms of cos(2pi/5) and Cos(pi/5)
    Cos(\frac{2\pi}{5})Cos(\frac{\pi  }{5}) + Cos(\frac{\pi}{5})Cos(\frac{3\pi  }{5}) + Cos(\frac{\pi}{5})Cos(\frac42\pi  }{5}) + Cos(\frac{2\pi}{5})Cos(\frac{3\p  i}{5})+Cos(\frac{2\pi}{5})Cos(\f  rac{4\pi}{5})+Cos(\frac{3\pi}{5}  )Cos(\frac{4\pi}{5})

    I have no idea where to even start as all the others were simply simplifying using trig graphs and the cast diagram.
    All help appreciated ! Thanks !
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    (Original post by Joteca)
    Hi !
    I'm struggling with the questions on some FP1 work I got as we haven't covered any of this in class. I've worked out how to do it all apart from this question:

    Express in terms of cos(2pi/5) and Cos(pi/5)
    Cos(\frac{2\pi}{5})Cos(\frac{\pi  }{5}) + Cos(\frac{\pi}{5})Cos(\frac{3\pi  }{5}) + Cos(\frac{\pi}{5})Cos(\frac42\pi  }{5}) + Cos(\frac{2\pi}{5})Cos(\frac{3\p  i}{5})+Cos(\frac{2\pi}{5})Cos(\f  rac{4\pi}{5})+Cos(\frac{3\pi}{5}  )Cos(\frac{4\pi}{5})

    I have no idea where to even start as all the others were simply simplifying using trig graphs and the cast diagram.
    All help appreciated ! Thanks !
    sry i cant help, but i need to ask....if u do FP1 on edexcel, and if ur doing it on the 2004 curriculum, where can i get a book and what does it look like?
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    consider the double angle formulae
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    (Original post by kcfch)
    consider the double angle formulae
    We've never done that. I don't even think it's in my formula book, could you tell me what it is please?
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    Have you done C1 - C4 ?
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    youre doing further maths and you havent covered double angle formulae?!
    its in C3... well anyway, its like this:
    cos (A+B) = cosAcosB - sinAsinB
    cos (A-B) = coaAcosB + sinAsinB
    sin (A+B) = sinAcosB + sinBcosA
    sin (A-B) = sinAcosB - sinBcosA
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    I've only done C1 and C2, this year I'm doing C3 C4 FP1-4 and D1 S1 and M2

    Thanks ! I should be able to do it now !
 
 
 
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