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Edexcel FP3 - 27th June, 2016 watch

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    (Original post by samb1234)
    How would you phrase the answer to this question? Jn is defined as Jn = integral between 0 and 2pi of cos^n x, with the reduction being nJn=cos^n-1 x sinx +(n-1)Jn-2. Basically you had to show if n is odd Jn is always equal to 0. I basically said that the only term independent of sine (as sine npi is 0) is the case where n =1, i.e. the integral of cosx so again you get sinx which when evaluated obviously gives you 0 again, but i wondered if there was a more eloquent way to show it.
    It looks inductionable, though an intuitive explanation would probably be fine.


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    Does anyone have a good structure/method to approach FP3 loci problems? It'd be much appreciated if you could share. It's the only area of FP3 I can't get my head around.
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    Model answers to all past papers can be found here:
    http://www.thestudentroom.co.uk/show...3#post64179673
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    (Original post by oinkk)
    Does anyone have a good structure/method to approach FP3 loci problems? It'd be much appreciated if you could share. It's the only area of FP3 I can't get my head around.
    Usually they ask you to find the locus of a point which they asked you to find in a previous part. The key is to express the X and Y coordinates as parametric coordinates. Then it's just eliminating variables to get an equation in X and Y.
    However, this won't always be doable. In this case, they usually ask you to show that the cartesian equation of the locus is given by blah blah blah. In this case it's easier to show that LHS = RHS (or vice versa) using the parametric coordinates you found.

    Have a look at examples from past papers, I have written model answers to all past papers here:
    http://www.thestudentroom.co.uk/show...3#post64179673
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    hello every one,
    can someone please explain to me q4 of chapter 2 mixed exercise as I forgot how I did before?
    many thanks
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    (Original post by M.green)
    hello every one,
    can someone please explain to me q4 of chapter 2 mixed exercise as I forgot how I did before?
    many thanks
    It would be easier for everyone if you posted the question or link the solution bank
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    (Original post by SeanFM)
    It would be easier for everyone if you posted the question or link the solution bank
    thanks for your respond
    but I don't get the answer to the part when they get the equation for PB^2
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    Anyone got any tips on how to go about reduction formulae questions? Most of them just require basic parts but alot of the exam q's I see require more than that.

    Like how would you spot certain clues to 'make it work?

    Like this one for example (Jun 15)

    I did this paper and attempted to use 1 as one part and the sin ^n x as the other but the mark scheme advises you to split it into

    Sin^n-1 x sin ^ x which makes sense but it's a case of how would I know to do that?

    I see the result has a n-2 in it which might indicate doing that as it'll differentiate to n-2 but so would doing parts twice on my initial method, which isn't uncommon.

    So yeah long story short, how'd you go about this.

    Oh and part (b)...what the hell


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    (Original post by CALI1198)
    Anyone got any tips on how to go about reduction formulae questions? Most of them just require basic parts but alot of the exam q's I see require more than that..
    It's most intuition you gain from practice, for example - you see that the integral has a n-2 in it and that should immediately get you thinking of two things:

    (i) IBP twice.
    (ii) split into x^(n-1) x.

    The latter case is motivated when you have something of the form

    x^n f(x) where f(x) is annoying and/or hard to integrate but xf(x) is stupendously easy to integrate.

    Furthermore to this, you have a

    (n-1)I_{n-2}, this should also alert you to the usage of splitting into x^(n-1) x^{n} instead of IBP twice, since with IBP twice you would expect something like (n-1)(n-2)I_{n-2} or (n-2)I_{n-2}.

    part (b) is just placing limits on your answer to part (a). The bottom limit is just obviously 0, the upper limit you need to remember is n is an odd number, so you need to stop at I_1. Then it's just a matter of plugging in x=pi/2 into your answer to part (a).

    Part (c) is just rewriting \cos^2 x = 1 - \sin^2 x and using the answer to (b) in two different cases with sin^5 and sin^7.
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    Argh, either Tapatalk or tsr has put Smiley's in there haha. I sort of get ya, plan to sit down and just work through loads of similar types

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    (Original post by CALI1198)
    Argh, either Tapatalk or tsr has put Smiley's in there haha. I sort of get ya, plan to sit down and just work through loads of similar types

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    Cheers, it should be viewable properly if you open TSR on your mobile browser instead of an app. Let me know if you need any help.
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    I have a few problems with vector actually, i can do the exercise and get it right but im not really sure how it works. So my skill only work if im lucky enough to get a straight forward question but not the complicated one. any tips ?
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    (Original post by anndz3007)
    I have a few problems with vector actually, i can do the exercise and get it right but im not really sure how it works. So my skill only work if im lucky enough to get a straight forward question but not the complicated one. any tips ?
    Some videos online might help as they'll probably give you an actual visual as to what is happening. Eg two planes intersecting, showing why the cross product of the two normals gives you the line of intersection.

    Vectors, the visual is the key to understanding it IMO.

    If possible, ask your teacher to help you with visualising. Might help you to appreciate the concepts more

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    Non syllabus stuff below.
    Does anyone know how to do intrinsic equations questions?
    For example, Q7 from this, http://old.antonymale.co.uk/s/downlo...2FP5%2FP5B.pdf.
    I can do part (a), it's just the derivative, \rho = \dfrac{\mathrm{d}s}{\mathrm{d} \Phi}.
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    (Original post by EricPiphany)
    Non syllabus stuff below.
    Does anyone know how to do intrinsic equations questions?
    For example, Q7 from this, http://old.antonymale.co.uk/s/downlo...2FP5%2FP5B.pdf.
    I can do part (a), it's just the derivative, \rho = \dfrac{\mathrm{d}s}{\mathrm{d} \Phi}.
    \displaystyle \frac{\mathrm{d}y}{\mathrm{d} \psi} = \frac{\mathrm{d}y}{\mathrm{d}s} \times \frac{\mathrm{d}s}{\mathrm{d} \psi} = \cdots
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    (Original post by EricPiphany)
    Non syllabus stuff below.
    Does anyone know how to do intrinsic equations questions?
    For example, Q7 from this, http://old.antonymale.co.uk/s/downlo...2FP5%2FP5B.pdf.
    I can do part (a), it's just the derivative, \rho = \dfrac{\mathrm{d}s}{\mathrm{d} \Phi}.
    It is old syllabus, I have the P5 book so I will send all the notes on it when i get home tmmrw it used to come up in M6 aswell, well applications of it


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    (Original post by Zacken)
    Cheers, it should be viewable properly if you open TSR on your mobile browser instead of an app. Let me know if you need any help.
    I ended up pulling the solution bank from PMT and attempting the questions on there. I've sort of got a method where I try splitting it first and if that fails, I try splitting something.

    Seems to have worked. That question I posted here makes perfect sense now! Cheers for the help

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    (Original post by Zacken)
    \displaystyle \frac{\mathrm{d}y}{\mathrm{d} \psi} = \frac{\mathrm{d}y}{\mathrm{d}s} \times \frac{\mathrm{d}s}{\mathrm{d} \psi} = \cdots
    Aha. And for the last part  \displaystyle x=\int \frac{\mathrm{d}x}{\mathrm{d}y} \,\mathrm{d}y = \int \cot(\psi) \, \mathrm{d}y =  \int \cot(y) \, \mathrm{d}y . Does that look reasonable?


    (Original post by physicsmaths)
    It is old syllabus, I have the P5 book so I will send all the notes on it when i get home tmmrw it used to come up in M6 aswell, well applications of it



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    Thanks.
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    (Original post by EricPiphany)
    Aha. And for the last part  \displaystyle x=\int \frac{\mathrm{d}x}{\mathrm{d}y} \,\mathrm{d}y = \int \cot(\psi) \, \mathrm{d}y =  \int \cot(y) \, \mathrm{d}y . Does that look reasonable?
    Yep, that's precisely correct.
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    (Original post by CALI1198)
    I ended up pulling the solution bank from PMT and attempting the questions on there. I've sort of got a method where I try splitting it first and if that fails, I try splitting something.

    Seems to have worked. That question I posted here makes perfect sense now! Cheers for the help

    Sent from my One using Tapatalk
    Cheers, sounds good. It's a really lovely topic; I used to do those questions before starting FP3 because they just made intuitive sense; glad it's clicked for you too.
 
 
 
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