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5 Mark Integration Question - Need Help.

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Got a question about Student Finance? Ask the experts this week on TSR! 14-09-2014
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    Question 3 http://pdf.ocr.org.uk/download/pp_10..._gce_4724.pdf?

    Mark Scheme
    http://pdf.ocr.org.uk/download/ms_10...0_gce_jan.pdf?

    What I did..

    I expressed cos2x in terms of cosx (because the question ask to but i can't relate to how it will help?)

    (cos2x+1)/2 = cos^2 x

    So i split the integral into --> (cos2x)(cos^2 x)^-1 --> (cos2x)(sec^2 x)

    I integrated cos2x and got (1/2)sin2x and integrated sec^2 x which is tanx

    I then multiplied both and got

    (1/2)sin2xtanx

    I then subd in my limits and my answer was nowhere near the answer in the MS. I have a feeling i did something wrong when i integrated?

    Thanks.
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    Can you use latex

    I cannot see what you have done
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    (Original post by jameslad)
    Question 3 http://pdf.ocr.org.uk/download/pp_10..._gce_4724.pdf?

    Mark Scheme
    http://pdf.ocr.org.uk/download/ms_10...0_gce_jan.pdf?

    What I did..

    I expressed cos2x in terms of cosx (because the question ask to but i can't relate to how it will help?)

    (cos2x+1)/2 = cos^2 x

    So i split the integral into --> (cos2x)(cos^2 x)^-1 --> (cos2x)(sec^2 x)

    I integrated cos2x and got (1/2)sin2x and integrated sec^2 x which is tanx

    I then multiplied both and got

    (1/2)sin2xtanx

    I then subd in my limits and my answer was nowhere near the answer in the MS. I have a feeling i did something wrong when i integrated?

    Thanks.
    Express the numerator as 2cos^2x - 1

    therefore you get 2cos^2x - 1 / cos^2x = 2 - 1/cos^2x then integrate

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