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    kinda ready ... i did soloman A-C and half of D and E .. i missed out the ones i didnt think were relevant ... didnt do brilliantly on them but not too bad either ..
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    best of luck you sexy people
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    Cheers lol
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    I am so underprepared it's not even funny.
    I feel like such a failure.
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    Can anyone actually do those rcos questions? :confused: They don't seem to make any sense to me at all. Is it too late for me to try to understand this
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    Give an example Katie and I'll see if I can explain it as fully as I can for you
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    Thanks!
    7. (a) (i) Show that
    sin (x + 30)° + sin (x − 30)° ≡ a sin x°,
    where a is a constant to be found.

    (ii) Hence find the exact value of sin 75° + sin 15°, giving your answer
    in the form 6(sqrt)b .

    (b) Solve, for 0 ≤ y ≤ 360, the equation
    2 cot2 y° + 5 cosec y° + cosec2 y° = 0.
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    7. (a)

     sin(x+30)+sin(x-30) = asinx

    You should know the identity for sin(A+B) and sin(A-B). Let's use them in this situation.

     sinxcos30 + cosxsin30 + sinxcos30 - sin30cosx
     =2sinxcos30
     = 2\frac{\sqrt{3}}{2}sinx
     =  \frac{2\sqrt{3}}{2}sinx
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    (b) Notice sin75+sin15 is given by putting x=45 into sin (x+30)° + sin (x- 30)° ≡ a sin x°

    Using our previous result:  \frac{2{\sqrt3}}{2}sinx
     \frac{2{\sqrt3}}{2}sin45

    From special triangles we know  sin45 = \frac{1}{\sqrt2}

    So ans  = (\frac{2{\sqrt3}}{2})(\frac{1}{\  sqrt2}
     = \frac{2{\sqrt3}}{2\sqrt2}
     = \frac{\sqrt3}{\sqrt2}
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    (Original post by Lusus Naturae)
    (b) Notice sin75+sin15 is given by putting x=45 into sin (x+30)° + sin (x- 30)° ≡ a sin x°

    Using our previous result:  \frac{2{\sqrt3}}{2}sinx
     \frac{2{\sqrt3}}{2}sin45

    From special triangles we know  sin45 = \frac{1}{\sqrt2}

    So ans  = (\frac{2{\sqrt3}}{2})(\frac{1}{\  sqrt2}
     = \frac{2{\sqrt3}}{2\sqrt2}
     = \frac{\sqrt3}{\sqrt2}
    Thank you so much
    So then you multiply both sides by sqrt2 and get the answer (I don't know how to use the tags, sorry).
    And thank you so much for than perfectly explained answer
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    mine as it 2pm. i'm just gonna relax, no more revision.
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    yeah i think im not gonna do anything else....need some rest to think properly.

    i am really nervous
    why did i have to do C3 this year
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    Im gonna read these C3 wiki notes then my formula sheet then Im sorted :>

    http://wikinotes.cdpuk.net/wiki/C3
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    Good luck everybody
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    ^^Thanks! And thank's for your help yesterday!
    Just a quick question. This identity is correct, right?

    cosex^[email protected] = 1 + [email protected]

    It's different on wikinotes http://wikinotes.cdpuk.net/wiki/C3_Formulae
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    yup
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    ahh, i'm nervous exams at 2:00
    good luck everybody
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    good luck everyone .. lets hope they make it a lot like june 2005 ... and give us nice qs .. :p: lol
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    hopefully exactly the same as june 2005
 
 
 
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