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    • Thread Starter
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    Hi,
    I'm currently doing OCR C4 Jan 09 and am having some difficulty with quesiton 4.
    It is to find the answer to the integration with limits 1/4 pi and 0 of (1 + sinx)^2.
    I've looked at the mark scheme but it just confused me more...
    If someone can talk me through how to do it, that'd be awesome
    Thanks.
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    You need to start with the identity \cos 2x = \cos^2 x - \sin^2 x

    Get \sin^2 x in terms of \cos 2x and so on.
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    (Original post by Mr M)
    You need to start with the identity \cos 2x = \cos^2 x - \sin^2 x

    Get \sin^2 x in terms of \cos 2x and so on.
    Surely first I expand (1 + sinx)^2 to get 1 + 2sinx + sin^2x, then if I use that identity to sub out sin^2x I get 1 + 2sinx + 1/2(1 - cos2x)...
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    (Original post by El Xando)
    Surely first I expand (1 + sinx)^2 to get 1 + 2sinx + sin^2x, then if I use that identity to sub out sin^2x I get 1 + 2sinx + 1/2(1 - cos2x)...
    If you like. That is correct.
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    (Original post by Mr M)
    If you like. That is correct.
    I'm still not sure how that helps me integrate it to find an exact value :P
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    (Original post by El Xando)
    I'm still not sure how that helps me integrate it to find an exact value :P
    Really? Presumably you know this ...

    \int \cos (ax + b) = \frac{\sin(ax + b)}{a} + k
 
 
 
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