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    Stuck on part c of this question, here's my working for all parts in case it proves relevant Name:  ImageUploadedByStudent Room1457133759.958125.jpg
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    Zacken
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    Sketch the graph and the cord, sketch the line 1-x then find and sketch the tangent. What do you observe?
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    (Original post by Zacken)
    Sketch the graph and the cord, sketch the line 1-x then find and sketch the tangent. What do you observe?
    the graph cos(x)-sin(x) is 'sandwiched' between the the chord and the line 1-x, tangent of what?
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    (Original post by drandy76)
    the graph cos(x)-sin(x) is 'sandwiched' between the the chord and the line 1-x, tangent of what?
    The chord is 1-x, isn't it? I'm in bed and don't have my glasses on but that's what it seems like to me. Tangent at p, what's the equation of the tangent at P?
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    (Original post by Zacken)
    The chord is 1-x, isn't it? I'm in bed and don't have my glasses on but that's what it seems like to me. Tangent at p, what's the equation of the tangent at P?
    y=-1(x-pi/4) rearranged to give me y=pi/4(1-4x/pi), not seeing how the cord is y=1-x with the intersection at pi/4, although i could be misreading
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    (Original post by drandy76)
    y=-1(x-pi/4) rearranged to give me y=pi/4(1-4x/pi), not seeing how the cord is y=1-x with the intersection at pi/4, although i could be misreading
    The chord is the line connecting P and Q, what's the equation of that?
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    (Original post by Zacken)
    The chord is the line connecting P and Q, what's the equation of that?
    been looking at not now, but it looks like the line y=1-4x/pi fits the criteria, which means i need to re look at the equation of the tangent EDIT: found the tangent form the wrong point, its y=1-x
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    (Original post by drandy76)
    been looking at not now, but it looks like the line y=1-4x/pi fits the criteria, which means i need to re look at the equation of the tangent EDIT: found the tangent form the wrong point, its y=1-x
    LOL. I can't read apparently. I thought the pi was something else

    So the curve being sandwiched gives rise to the inequality
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    (Original post by Zacken)
    LOL. I can't read apparently. I thought the pi was something else

    So the curve being sandwiched gives rise to the inequality
    Yeah this question is actually pretty neat , although it would be a bit s*** to get this in under exam conditions
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    (Original post by drandy76)
    Yeah this question is actually pretty neat , although it would be a bit s*** to get this in under exam conditions
    Sounds very part (i) of a STEP question-esque. I know of one that uses the same concept as this in a very different context, you'd enjoy it. Remins me tomorrow, I'm in bed now.

    Edit: don't think you'd get something like thisnis an exam. :dontknow:
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    (Original post by Zacken)
    Sounds very part (i) of a STEP question-esque. I know of one that uses the same concept as this in a very different context, you'd enjoy it. Remins me tomorrow, I'm in bed now.

    Edit: don't think you'd get something like thisnis an exam. :dontknow:
    will do, PRSOM it has ocr at the bottom, which means they put it in an exam although it has an asterix so they must have felt it was too hard when everyone's scores plummeted
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    (Original post by drandy76)
    will do, PRSOM it has ocr at the bottom, which means they put it in an exam although it has an asterix so they must have felt it was too hard when everyone's scores plummeted
    Possibly it was in an exam a few years ago when standards were higher or such. The edexcel textbook is the same! They have "examination question" that make recent papers look a doddle.
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    (Original post by Zacken)
    Possibly it was in an exam a few years ago when standards were higher or such. The edexcel textbook is the same! They have "examination question" that make recent papers look a doddle.
    Wouldnt mind a return to those standards, A's for FP2/3 are already ~55/72 going even further down gives me more room for silly errors
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    (Original post by drandy76)
    Wouldnt mind a return to those standards, A's for FP2/3 are already ~55/72 going even further down gives me more room for silly errors
    A year or two ago, it was 71/75 for an A* in FP2... wtf. :afraid:
    Even this Jan, the S2 exam that I sat, it was 70/75 for an A*...
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    (Original post by Zacken)
    A year or two ago, it was 71/75 for an A* in FP2... wtf. :afraid:
    Even this Jan, the S2 exam that I sat, it was 70/75 for an A*...
    Those UMS jumps are horrendous, congrats on your results btw, as for M3.... luckily you took s3 as an insurance
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    (Original post by Zacken)
    A year or two ago, it was 71/75 for an A* in FP2... wtf. :afraid:
    Even this Jan, the S2 exam that I sat, it was 70/75 for an A*...
    http://filestore.aqa.org.uk/over/sta...-JUNE-2015.PDF

    Greatest exam board ever
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    (Original post by drandy76)
    Those UMS jumps are horrendous, congrats on your results btw, as for M3.... luckily you took s3 as an insurance
    Yeah, I don't know what exam boatds are playing at nowadays. :erm:
    Thanks! I only picked up S3 'cause I knew I flunked M3.

    Darn.
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    (Original post by Zacken)
    Sketch the graph and the cord, sketch the line 1-x then find and sketch the tangent. What do you observe?
    I guess that they're looking for a graphical approach, given that this is an A level question, though the question doesn't make it clear. I think that you can also show that the inequality holds by considering the gradient of \cos x-\sin x=\sqrt{2}\cos(x+\frac{\pi}{4}) over the interval, though I found the argument for the lower inequality tricky to get right (late last night, at least).
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    (Original post by atsruser)
    I guess that they're looking for a graphical approach, given that this is an A level question, though the question doesn't make it clear. I think that you can also show that the inequality holds by considering the gradient of \cos x-\sin x=\sqrt{2}\cos(x+\frac{\pi}{4}) over the interval, though I found the argument for the lower inequality tricky to get right (late last night, at least).
    That's a nice analytic approach. I was looking into getting the inequality bounds by looking at the Laurent series for the function and deducing then from there but I don't have quite enough experience to know whether that's viable or not.
 
 
 
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