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    http://pastpapers.download.wjec.co.uk/s15-0978-01.pdf
    Can someone help me with 3bi? Ive done part a
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     n=0 ? From De Moivre's theorem. Just look for smallest n to make sin(3pi/4 * n) = 0 as this makes the imaginary part equal 0
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    (Original post by RDKGames)
     n=0 ? From De Moivre's theorem. Just look for smallest n to make sin(3pi/4 * n) = 0 as this makes the imaginary part equal 0
    Ahhh okay thanks and what about for bii?
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    (Original post by Ayaz789)
    Ahhh okay thanks and what about for bii?
    Same idea, look for smallest integer n to make the real part equal zero, so for which smallest n will cos(3pi/4 * n) = 0 ?

    Also, how do I use fractions on this site? I'm new xD
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    (Original post by RDKGames)
    Same idea, look for smallest n to make the real part equal zero, so for which smallest n will cos(3pi/4 * n) = 0 ?

    Also, how do I use fractions on this site? I'm new xD
    Haha i dont use latex much but you can ask the person i tagged! Thanks for your help
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    (Original post by RDKGames)
    Same idea, look for smallest integer n to make the real part equal zero, so for which smallest n will cos(3pi/4 * n) = 0 ?

    Also, how do I use fractions on this site? I'm new xD
    http://www.thestudentroom.co.uk/wiki/LaTex

    This page has everything you need to know.

    To use fractions, \frac{a}{b} for \frac{a}{b} and \dfrac{a}{b} for a bigger \dfrac{a}{b}.

    Also you might like to know that for Greek letters such as \pi, just a \ before the name of the letter (and generally a \ before a lot of things such as \cos\theta to give \cos\theta for example).
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    (Original post by IrrationalRoot)
    http://www.thestudentroom.co.uk/wiki/LaTex

    This page has everything you need to know.

    To use fractions, \frac{a}{b} for \frac{a}{b} and \dfrac{a}{b} for a bigger \dfrac{a}{b}.

    Also you might like to know that for Greek letters such as \pi, just a \ before the name of the letter.
    Ah thanks, exactly what I was looking for!

    (Original post by Ayaz789)
    Haha i dont use latex much but you can ask the person i tagged! Thanks for your help
    No problem OP, got my FP2 exam tomorrow morning so I gotta stay sharp with this stuff as well!
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    (Original post by RDKGames)
    Ah thanks, exactly what I was looking for!



    No problem OP, got my FP2 exam tomorrow morning so I gotta stay sharp with this stuff as well!
    Haha ohh , ive got mine tomorrow too , i dont think im ready though haha
    http://pastpapers.download.wjec.co.uk/s15-0978-01.pdf
    Okay so in q4? Id normally use my general solutions method if it was costheta + cos3theta or something , but what do i do with the Pi/6 inside the bracket?
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    (Original post by Ayaz789)
    Haha ohh , ive got mine tomorrow too , i dont think im ready though haha
    http://pastpapers.download.wjec.co.uk/s15-0978-01.pdf
    Okay so in q4? Id normally use my general solutions method if it was costheta + cos3theta or something , but what do i do with the Pi/6 inside the bracket?
    My first instinct is to use the double angle formula for cos and factor out trig on pi/6. I'll have a go and see for myself.
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    (Original post by RDKGames)
    My first instinct is to use the double angle formula for cos and factor out trig on pi/6. I'll have a go and see for myself.
    Ah okay sure
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    (Original post by RDKGames)
    My first instinct is to use the double angle formula for cos and factor out trig on pi/6. I'll have a go and see for myself.
    I cant do it , & neither do i understand the ms tbh! http://www.wjec.co.uk/qualifications...pastpaper=true
    The ms if you cant do it:/ if you can do it then please explain it to me! Well ive done the first 2 marks of it
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    (Original post by Ayaz789)
    I cant do it , & neither do i understand the ms tbh! http://www.wjec.co.uk/qualifications...pastpaper=true
    The ms if you cant do it:/ if you can do it then please explain it to me! Well ive done the first 2 marks of it
    The mark scheme makes sense however I'm having difficulties getting rid off cosines. I have cos(3x)+cos(2x)+cos(x) + sin(3x)+sin(2x)+sin(x) = 0 but they don't touch upon cos at all?
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    (Original post by RDKGames)
    The mark scheme makes sense however I'm having difficulties getting rid off cosines. I have cos(3x)+cos(2x)+cos(x) + sin(3x)+sin(2x)+sin(x) = 0 but they don't touch upon cos at all?
    I really dont know :/ Seems like a very weird question ngl
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    (Original post by Ayaz789)
    I really dont know :/ Seems like a very weird question ngl
    I have the solutions however I did differently to the mark scheme. Instead, I used the following identity:

     cos(A)+cos(B)=2cos(\frac{A+B}{2}  )cos(\frac{A-B}{2})

    Now, I let A=x+\frac{\pi}{6} and B=3x+\frac{\pi}{6}

    So after applying the identity and tidying things up, I ended up with:

    2cos(2x+\frac{\pi}{6})cos(-x)+cos(2x+\frac{\pi}{6})=0

    Now remember that cos(-x)=cos(x) and that you can factor out cos(2x+\frac{\pi}{6}). At this point just solve the two products equaling 0 and you should get 3 general solutions.

    For x=2n\pi \pm \frac{2\pi}{3} you can just ignore the plus sign one because those solutions are covered by one of the other two for later values of n.

    Oh, and this is definitely the weirdest general solution question I've come across, nothing like this popped up with AQA and general solutions are done in FP1. Plus this is the first time I made use of that identity lol.
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    (Original post by RDKGames)
    I have the solutions however I did differently to the mark scheme. Instead, I used the following identity:

     cos(A)+cos(B)=2cos(\frac{A+B}{2}  )cos(\frac{A-B}{2})

    Now, I let A=x+\frac{\pi}{6} and B=3x+\frac{\pi}{6}

    So after applying the identity and tidying things up, I ended up with:

    2cos(2x+\frac{\pi}{6})cos(-x)+cos(2x+\frac{\pi}{6})=0

    Now remember that cos(-x)=cos(x) and that you can factor out cos(2x+\frac{\pi}{6}). At this point just solve the two products equaling 0 and you should get 3 general solutions.

    For x=2n\pi \pm \frac{2\pi}{3} you can just ignore the plus sign one because those solutions are covered by one of the other two for later values of n.

    Oh, and this is definitely the weirdest general solution question I've come across, nothing like this popped up with AQA and general solutions are done in FP1. Plus this is the first time I made use of that identity lol.
    Haha thank you so much! Top guy lol
 
 
 
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