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    Integration advice needed

    Yeah, you may want to pre-derive that formula before setting out to tackle an integral like this so that you have it handy if you need it.
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    Integration advice needed

    Oh sorry lol, I was thinking of a sec rather than sec^2 being the thing expanded. $\noindent If we have $\sec^m x\tan ^n x$, where $m$ is an odd positive integer and $n$ is an even positive integer, then $n =2k$ for some positive integer $k$ and so $\tan ^n x = \left(\tan ^2 x\right)^k =...
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    Integration advice needed

    $\noindent Say $I = \int \sec ^5 x \tan^ 4 x \text{ d}x$. Then $\tan^4 x = \left(\sec^2 x-1\right)^2$. So $I = \int \sec ^5 x \left(\sec^2 x-1\right)^2\text{ d}x$. Expanding this via the binomial theorem will give us some terms with an even (and some with odd) power of $\sec x$.$
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    Integration advice needed

    I'm afraid this case is the most tedious of the bunch.
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    Help me decide :P

    If you plan on studying something that requires maths at university, you should probably not do General (if possible).
  6. I

    Matrices question

    Yeah it won't hold if M can be any real matrix at all (edited in an example). If they meant for M to have integer entries, then you can show the n = 2 case using Cayley-Hamilton theorem for instance. The characteristic polynomial will be pM(z) = z2 + bz + c, where b and c are integers (you can...
  7. I

    Matrices question

    $\noindent Hint: It can be done quite easily by induction (show it starting from $n=1$, since this is an easy base case, and you can use strong induction if needed). :-). Doing it this way will also be able to give you a recursive formula for the $a_n$ and $b_n$, assuming you are able to find...
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    Prelim 2016 Maths Help Thread

    $\noindent For the upper half of a circle of radius $a$ ($a$ some constant greater than $0$), we can write it as $y=\sqrt{a^2-x^2}$, $-a<x<a$. Then $y^\prime = \frac{-x}{\sqrt{a^2-x^2}}$, for $-a<x<a$. You can do a similar computation for the lower half, where $y=-\sqrt{a^2-x^2}$ $\Big{(}$well...
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    2016ers Chit-Chat Thread

    Probably the definition of ''definition''.
  10. I

    Equation of a locus- help!

    If the midpoint lies on the unit circle, then P must be 2 units from O. Conversely if P is 2 units from O, the midpoint lies on the unit circle. Hence the desired locus is the circle of radius 2 centred at the origin, i.e. x2+ y2= 4.
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    Prelim 2016 Maths Help Thread

    $\noindent The discriminant is $\Delta = \left(k+1\right)^2 - 4\left(2k-3\right)\cdot (-1) = k^2 + 2k + 1 + 8k - 12 = k^2 + 10 k\, \color{blue}{ - 11}$ (rather than your $-10$). This factors into $\Delta = \left(k+11\right)\left(k-1\right)$, and so the given answers are right.$
  12. I

    "Assess" Keyword

    Well the HSC definition for "Assess" is "Make a judgement of value, quality, outcomes, results or size" ( http://www.boardofstudies.nsw.edu.au/syllabus_hsc/glossary_keywords.html ), so you should give a final judgement of whether it is overall a positive impact or negative impact. So probably...
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    Is this justified to lose a mark?

    Now that really is quite strange (but probably typical of HSC Science).
  14. I

    Is this justified to lose a mark?

    It's pretty common in HSC Science to lose marks for things like this (not closing tables, or not drawing the lines in ruler, etc.).
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    Quick question: High internal rank and cohort, low external HSC mark

    One can find full details of the quadratic interpolation procedure used for the moderation of school marks in the attachment in this comment: .
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    Quick question: High internal rank and cohort, low external HSC mark

    I was intentionally using the word "scaling" to refer to a general adjustment procedure.
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    Quick question: High internal rank and cohort, low external HSC mark

    The scaling process isn't that simple though is it (I.e. your internal mark that'll get used isn't in general simply P% of E1)?
  18. I

    Prelim 2016 Maths Help Thread

    $\noindent Except if $x = -1$, when the answer is $\ln |e|+ \mathcal{C}$. :$\mathcal{P}$$
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    HSC 2016 MX1 Marathon (archive)

    Re: HSC 2016 3U Marathon $\noindent Let $P$ be the point $\left(a,b\right)$ in the Cartesian plane. Let $P^{*}$ be the point obtained by reflecting $P$ about the line $y=x$. Show that $P^{*}$ has coordinates $\left(b,a\right)$.$
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    IB Maths Marathon

    Re: International Baccalaureate Marathon 2016 So basically (making the approximating assumption that these countries all have roughly same proportion of their total population be of Year 12 (or equivalent) age), the US has a larger ratio of its students doing the IB compared to UK (and also...
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