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    (Original post by sulexk)
    hey there guys just wondering, any ideas on how many raw marks needed to get 100% in the last couple of years?

    thanks!
    It's normally around 72-73 / 75.
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    thank you!
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    (Original post by Noble.)
    0% of the people I spoke to had an issue with that question.
    Speaking to no one doesn't count lol
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    (Original post by xSkyFire)
    Speaking to no one doesn't count lol
    hahaha, classic
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    (Original post by crazedmonkey09)
    Under the pressure of an exam things look very different, there were many things that made me think to do that, the unusually high marks for it - it must be complex which it certainly wasn't differentiate tan, use identity, dy/dx = 1/dx/dy i'm counting 3 steps there

    Certainly in the way they used x and y again suggests replace this with this.
    If it didn't say 'given that' there wouldn't be a problem.
    But people make mistakes on all lots of questions in the exam that they would normally get right, this isn't any different.

    The use of given that in this question is perfectly reasonable as is using x and y which are the standard unknown in Mathematics for these types of equations. In fact I would say more students would have found it more confusing if they had used different letters.
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    does anyone have the paper?
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    look on page 31 to 33
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    Wow I thought I was the only one who did the same thing for the tany question. I left it out and came back to it with 30 mins to spare, and used up the whole three pages and got very annoyed after a while. I could've used that time to check my answers for other questions.

    What annoyed me more was that this was worth 5 marks, and when I got out of the exam and found out how to do it, it was so incredibly simple, a lot more easier than what I was trying to do, how could that be worth 5 marks?

    It was a very badly worded question.
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    Well if TSR peeps can make that mistake, I'm sure many others made the same mistake.

    Low boundaries! =D
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    (Original post by tiny hobbit)
    Yes the solutions include 45. Try using your brain instead of your calculator when checking your solutions.

    If you sketch the graph of y=cot t, it crosses the t-axis at 90, i.e. it equals 0 when t = 90 (I chose t to avoid confusion between x and 2x).
    haha but my brain fails in exam conditions... I should have realised there were two more solutions on the basis it was a 7 mark question. oh well never mind.
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    (Original post by crazedmonkey09)
    There are 25 other letters they could have used, they could have phrased it differently, they could have even separated it more clearly i.e instead of it being 4ii) which almost certainly links to 4i) they could have made it 4b.
    I also started subbing it in and got a complete mess of an equation thanks to their dodgy wording. Why the hell was it worth 5 marks when its was just 3 parts of working! I just can't get my head around it, its as if 1 mark was for knowing c4 arctan differentiation and the other was for avoiding strong hints.
    completely agree
    this whole session, in all my maths modules they have been making questions unclear with this i and ii business.
    5 marks for do dx/dy then looking in a formula book, its insane.
    A lot of people got this question wrong purely for the examinors not making the question clear enough, im hoping they exclude this question from the ums marks, or do anything to rectify thier mistakes
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    LOOL i can't believe C3 discussion is still ongoing.
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    (Original post by Noble.)
    0% of the people I spoke to had an issue with that question.
    :rofl: :rofl: what 0%?
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    I agree that the question is very clear:

    Part (i) Given that y = .... , find dy/dx.

    Part (ii) Given that x = tan(y), find dy/dx.

    It couldn't be any clearer!!
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    (Original post by Remarqable M)
    :rofl: :rofl: what 0%?
    that joke's been done (better)
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    (Original post by Zacula)
    I agree that the question is very clear:

    Part (i) Given that y = .... , find dy/dx.

    Part (ii) Given that x = tan(y), find dy/dx.

    It couldn't be any clearer!!
    exactly! the only way a question is related to the next one is if they use words like hence, or otherwise.
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    Looking at that now, I could understand people getting a little mislead because of the use of the same notation.

    Maybe y should have = \theta instead but to use y AND x for the second question could have caused problems

    If a lot of people are getting this wrong too, added to the other ones, this may mean amazingly low grade boundaries!!
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    Guys, if you express y w.r.t. x you have y = Arctan(x). There is a reason why it is expressed in this form. The reason is that you later learn to remember by heart that d / dx [Arctan(x)] = 1 / (1+x^2).

    According to my opinion this is an excercise that should be done in class, and it should be so trivial, and should be included in the syllabus.

    This is a very useful result to be used in Integration later on.

    BUT, this is the easier form of such a question there could ever be. In a past paper of recent years (2006 or 2007) there was a very similar question, with x = sec(y) I think... So, in case you have already met this question and solved it (or had it solved), there is absolutely no reason why you should think that this was a hard question, or confusing.
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    I got to dy/dx = 1/sec^2y

    Then I subbed in y=arctanx

    :p:
    • Thread Starter
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    I forgot the identity linking tan and sec^2 so I drew a triangle and found cosy and then sec^2[y] =)
 
 
 
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