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    Thank you so much . I thought I had blown my chances at gettin the B because C3 went awful .
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    (Original post by kingaaran)
    No, I'm not asking the first.

     \frac{2}{cos(2y)+1} = \frac{2}{cos^2(y)-sin^2(y)+1}

     \frac{1}{cos^2(y)}

    But I can't see how that equals cos^2(y), like the person I quoted.

    I'm not confused with the identities or how to integrate, I'm sure I'm competent with that, but I'm not sure how cos^2(y) = \frac{2}{cos(2y)+1}?


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    They didn't say that? They said \displaystyle sec^2(y) = \frac{2}{cos(2y)+1}
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    (Original post by rayquaza17)
    They didn't say that? They said \displaystyle sec^2(y) = \frac{2}{cos(2y)+1}
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    By implication, this suggests that they are referencing cos^2(y), right?


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    (Original post by kingaaran)
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    By implication, this suggests that they are referencing cos^2(y), right?


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    I think monii was incorrect when they said about integrating cos^2(y) because you can actually integrate that, but you don't have to do that in this question. (Sorry monii)

    Post 993 has the correct answer for this question.
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    (Original post by kingaaran)
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    By implication, this suggests that they are referencing cos^2(y), right?


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    Not sure how well this has come out by hope it's of use.
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    (Original post by rayquaza17)
    I think monii was incorrect when they said about integrating cos^2(y) because you can actually integrate that, but you don't have to do that in this question. (Sorry monii)

    Post 993 has the correct answer for this question.
    To rectify, the only way to integrate cos^2(y) is by using the double angle formulae, or is there another 'FP3' method?



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    (Original post by NikolaT)
    Not sure how well this has come out by hope it's of use.
    Oh, you were talking about the integral of 1/cos^2(y)


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    (Original post by kingaaran)
    To rectify, the only way to integrate cos^2(y) is by using the double angle formulae, or is there another 'FP3' method?

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    Yes only sensible way is the double angle formula.
    I can think of only one other way to integrate it, but that involves complex numbers which is FP2. Tbh I think the double angle formula is easier in this case.
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    Hi, can anyone tell me how to do 6(a) from Solomon A? The markscheme isn't very helpful. (not sure why 2sin3xsin2x = cosx-cos5x)


    Thanks.
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    (Original post by JamGrip)
    Hi, can anyone tell me how to do 6(a) from Solomon A? The markscheme isn't very helpful. (not sure why 2sin3xsin2x = cosx-cos5x)


    Thanks.
    cos(x) = cos(3x - 2x)
    cos(5x) = cos(3x + 2x)

    Does that help?
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    So I'm thinking I got 69 + method marks on the C3 paper, so what do people think I'll need roughly for the A*? Aiming for low-mid 60s I think to be safe
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    (Original post by RobHunter97)
    So I'm thinking I got 69 + method marks on the C3 paper, so what do people think I'll need roughly for the A*? Aiming for low-mid 60s I think to be safe
    Depends on the paper bro


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    (Original post by physicsmaths)
    Depends on the paper bro


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    Obviously, but I mean approximately. 50s, 60s etc.
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    (Original post by RobHunter97)
    Obviously, but I mean approximately. 50s, 60s etc.
    60s
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    (Original post by anonwinner)
    60s
    Thank you
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    (Original post by kingaaran)
    To rectify, the only way to integrate cos^2(y) is by using the double angle formulae, or is there another 'FP3' method?



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    by parts is another way ...
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    Hi, can anyone explain why integrating 6/x is 6lnx and not ln6x? Thanks
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    (Original post by mdc96)
    Hi, can anyone explain why integrating 6/x is 6lnx and not ln6x? Thanks
    check by differentiation ...
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    (Original post by mdc96)
    Hi, can anyone explain why integrating 6/x is 6lnx and not ln6x? Thanks
    If you differentiate ln(6x), it becomes 6/6x which cancels to 1/x. Therefore 6x must become 6ln(x) if you integrate
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    (Original post by rayquaza17)
    Yes only sensible way is the double angle formula.
    I can think of only one other way to integrate it, but that involves complex numbers which is FP2. Tbh I think the double angle formula is easier in this case.
    no... you can use integration by parts...in a cunning way
 
 
 
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