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# Edexcel C3,C4 June 2013 Thread watch

1. holy moly why is the jan13 MS confusing as hell
2. (Original post by Rockit)
Just a question..

for Cartesian equations can they contain inverse trig functions?, it's much easier to find the parameter in terms of X or Y
eg,

y=sin t. X=cos t

cos^-1 = t

therefore Y=sin((cos^-1(t))
If they only ask for a Cartesian equation, then you can do that (don't write t instead of x in the exam though). If they ask for the equation in the form y = f(x), then, of course, you can't.

EDIT: Oh, wait, you can in this case. But in general, check exactly what they ask for.
3. (Original post by Theafricanlegend)
sin4x/2 ?
Correct
4. Oh god I hate maths I just wanna get this over ad done with!
going to go through all the past papers quickly, learn all the integration stuff, then get a good sleep, wake up at 6, review all integration stuff, and I'm done for maths!

It's particularly annoying when I probably can't answer any of the questions people are asking on thsi thread, making me seriously panic about this exam. D:

Getting a little bit stressed out atm, but hopefully a good night sleep will sort that out!

Good luck all!
5. (Original post by PoorLoser)
Oh god I hate maths I just wanna get this over ad done with!
going to go through all the past papers quickly, learn all the integration stuff, then get a good sleep, wake up at 6, review all integration stuff, and I'm done for maths!

Getting a little bit stressed out atm, but hopefully a good night sleep will sort that out!
Same. It's really getting to me.

Good luck!
6. Solomon paper L first question, why does the minimum number of people in the queue mean we need to make dn/dt = zero ?!?! Can anyone explain? I swear dn/dt is the rate of increase of people in the queue not the actual number of people in the queue?
7. (Original post by hilo36)
Hi dear you can you use the double angle formula for that problem

you have to carry out the following calculations
As we know that Sin(2X)=2sin(x)cos(x) but in your case we have got Sin2xcox2x so we just need to replace 2x with 4x as follows

Sin(4x)=2sin(2x)cos(2x) and then rearrange to get Sin(4x)/2=sin2sxcox2x

and then integrate Sin4x/2 and u will get -cos4x/8.
hope that make sense
8. If it wasn't for the C3 exam, I'd be feeling a lot less edgy right now... ah well, at least it's nearly over!
9. Are there any proofs needed for this exam?
10. (Original post by Rockit)
Just a question..

for Cartesian equations can they contain inverse trig functions?, it's much easier to find the parameter in terms of X or Y
eg,

y=sin t. X=cos t

cos^-1 x= t

therefore Y=sin((cos^-1(X))
Corrected it. But generally ms dont like it..
11. (Original post by Theafricanlegend)
Solomon paper L first question, why does the minimum number of people in the queue mean we need to make dn/dt = zero ?!?! Can anyone explain? I swear dn/dt is the rate of increase of people in the queue not the actual number of people in the queue?
The derivative is zero at minimums and maximums. You are looking for a minimum.
12. (Original post by Theafricanlegend)
Corrected it. But generally ms dont like it..
Thanks for correcting, if the question said find this cartesian in the form Y=f(x)

Could I use this inverse trig format?
sorry if its a stupid question !
13. Anyone els find the wordy differential equations really confusing?
14. Which of the past papers has the lowest grade boundaries??
15. Hi guys, i'm ready for this exam but theres one thing that always trips me. When solving differential equations, what side do you gather constants on? E.G dx/dt=15(5x-1) ...do you re-arrange to 1/15(5x-1) dx=dt

or 1/(5x-1) dx = 15dt
16. (Original post by Rockit)
Just a question..

for Cartesian equations can they contain inverse trig functions?, it's much easier to find the parameter in terms of X or Y
eg,

y=sin t. X=cos t

cos^-1 x= t

therefore Y=sin((cos^-1(t))
I'm not sure if they'd accept something like that.

It would be easier to just use a trig identity here:

So a basic equation of a circle.
17. Sometimes I honestly get a negative answer for integration and I know I have done it correctly. Do I just make it positive?

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18. (Original post by help-me333)
Hi guys, i'm ready for this exam but theres one thing that always trips me. When solving differential equations, what side do you gather constants on? E.G dx/dt=15(5x-1) ...do you re-arrange to 1/15(5x-1) dx=dt

or 1/(5x-1) dx = 15dt
It doesn't matter, constants can be taken outside of integrals, so do whatever's easiest.
19. (Original post by Sikkie)
Are there any proofs needed for this exam?
I think you need to prove a^x derivative is a^x(lna)
20. (Original post by noeliah4)
Does any1 knw how to do tht
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