Edexcel C3,C4 June 2013 Thread

holy moly why is the jan13 MS confusing as hell

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.

Reply 5042

MathsNerd1

17

Original post by Theafricanlegend

sin4x/2 ?

Correct

Reply 5043

PoorLoser

2

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!

(edited 10 years ago)

Reply 5044

senz72

19

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!

(edited 10 years ago)

Reply 5045

Theafricanlegend

15

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?

Reply 5046

fahmad1

Original post by hilo36

integrate Sin(2X)Cos(2x) please help

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 :biggrin:

Reply 5047

pjanoo

2

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!

Reply 5048

Sikkie

Are there any proofs needed for this exam?

Reply 5049

Theafricanlegend

15

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..

Reply 5050

OneMorePanda

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.

Reply 5051

Rockit

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 !

Reply 5052

joereed

Anyone els find the wordy differential equations really confusing?

Reply 5053

Exotica

Which of the past papers has the lowest grade boundaries??

Reply 5054

help-me333

12

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

Reply 5055

justinawe

19

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:

\cos^2 t + \sin^2 t = 1 \ \Rightarrow \ x^2 + y^2 =1

So a basic equation of a circle.

Reply 5056

cooldudeman

18

Sometimes I honestly get a negative answer for integration and I know I have done it correctly. Do I just make it positive?

Posted from TSR Mobile

Reply 5057

OneMorePanda

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.