C4 Jan 12 Edexcel Post Exam Discussion - Solutions in first post

I will update this first post on the day following the exam to upload the paper and model answers.

I do not have access to the papers before the exam

Here is a link to the June 11 thread, the first few posts contains stacks of useful stuff such as past papers, model answers, boundaries, hints and tips...

Scroll down to post #39

http://www.thestudentroom.co.uk/showthread.php?t=1619107&post=39

I know that to find solids of revolution, you have to do pi ∫ y^2 dx, but is there any instance where you'd have to do pi ∫ x^2 dy? Or am I just talking absolute rubbish..

Hi I realise this exam is only hours away, but I'd be grateful if anyone could answer these questions:


First, is it possible that the exam would ask us to find a definite integral (ie area under a curve) and then as a second part of the question ask us to use this area to find the volume? How would this be done without starting from scratch with : pi ∫ y^2 ?

Second, in the textbook exam style paper, there is a question that requires us to arrange secx/tan^2x into cosecxcotx using identity 1+tan^2x=sec^2x . How can this be done? The MS said it was only one step and one mark, but I can't figure it out at all!


Thanks and good luck everybody! Hopefully we don't get another 96% for A*!

secx/tan(^2)x = 1/[cosx(1-sec(^2)x)]

I give up D:

Aaaarggghhhh I got 33/75 on last year's paper just now I guess this is another summer resit


Edit: Sorry for wasting your time thinking someone answered your qu btw, shouldn't have quoted you

GOOD LUCK to everyone taking core 4 tomorrow ! There wont be many of us either i suppose ... fingers crossed its a good paper !

If everyone else doing the paper gets good luck, it will also mean bad luck to everyone because the grade boundaries would be ridiculously high, so nothing would change

But if everyone gets enough good luck that everyone gets 100%, then that's guaranteeing them 100% UMS too, so it doesn't matter how the grade boundaries change then

Mind you, my chances of getting 100% on the paper are as good as the chances of me getting into Oxbridge

Can anyone give me advice on how to get an a* for tomorrow. Currently I am getting 80% which is around 60, but since the grade boundaries are most probably going to be much higher than this what shall I do to prepare from today until tomorrow in order for me to get the best grade possible.

Maybe do past paper qus on the 20% you're not quite getting right?
Use mymaths or khanacademy, m4ths.com etc..to go over the concepts too

The spec says: pi ∫ y^2 dx is required, but not pi ∫ x^2 dy. Students should be able to find a volume of revolution, given parametric equations.
(For rotation about the y-axis you would do pi ∫ x^2 dy, but this isn't on the specification.)

I know that to find solids of revolution, you have to do pi ∫ y^2 dx, but is there any instance where you'd have to do pi ∫ x^2 dy? Or am I just talking absolute rubbish..

I asked my teacher about this earlier today and she said that revolutions about the y axis are only covered in Further Maths, not C4. So we only need to worry about pi ∫ y^2 dx

why cant u integrate (Sinx)^2 normally? Why do we have to change it to cos2x??? thanks.