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# Official Edexcel C3 Discussion Thread watch

1. (Original post by unknownking321)
the song i'm looking for may have actually been something like 'nanana' and the clapping sounds like the first few seconds of this song
2. http://www.wolframalpha.com/input/?i=d%2Fdx+lnx%2Ftanx

that should help out ^
3. (Original post by Doughboy)
How's it going everyone?

8 days left

EDIT: Someone please explain to me why the derivative of:

is

I can work out the answer, except that I don't get the x into sec^2x part
Using the quotient rule:

(Tell me if you don't understand this)

Now multiply all the terms by x:

----

Here's a question for you all from an Edexcel paper:

(I know the answer - just curious as to how many people can do this)

Given that:

y=arccosx -1<x<1 and 0<y<pi

a. Express arcsinx in terms of y

(Don't just copy the solution from the markscheme)
4. (Original post by MIKE ESSIEN IS QUITE SICK)
doing solomon papers is demotivating
Yes. Yes it is. I never start a solomon paper with the intention to finish it. I pick out the questions I know I would have trouble with in the exam and sit there until I find a solution.

Personally, if the exam is as much of a doddle as the C3 that people did in June 2009, im not worried. We just did a mock and I got 100%.

I seriously doubt it will be though .
5. (Original post by PurpleMonkeyDishwasher)
CSS - Alala? Not sure if there's clapping in that though. I'll give it some thought and probably get back to you...
(Original post by Girl Overboard)
nope thanks for trying.
6. (Original post by milliondollarcorpse)

Here's a question for you all from an Edexcel paper:

(I know the answer - just curious as to how many people can do this)

Given that:

y=arccosx -1<x<1 and 0<y<pi

a. Express arcsinx in terms of y

(Don't just copy the solution from the markscheme)
could you tell me what paper it's from? (I want to see whether i'm right/wrong and do the rest of the paper. )
7. (Original post by unamed)
could you tell me what paper it's from? (I want to see whether i'm right/wrong and do the rest of the paper. )
Jan 2007 It was only 3 marks so don't worry if you couldn't do it, and I think the paper had a relatively low grade boundary.
8. (Original post by milliondollarcorpse)
Jan 2007 It was only 3 marks so don't worry if you couldn't do it, and I think the paper had a relatively low grade boundary.
thank you! It just gives me something to go over, I find C3 worryingly easy.
9. Can someone give me some tips for finding the minimum or maximum possible value of Rcos([email protected]) or Rsin([email protected]) questions and how to determine value of x which gives the min/max value? I always fall down here
10. (Original post by Doughboy)
Can someone give me some tips for finding the minimum or maximum possible value of Rcos([email protected]) or Rsin([email protected]) questions and how to determine value of x which gives the min/max value? I always fall down here
well +R is always max value and -R is always min value.

for the second part, you have to equal sin(x+a) to 1. then you can get the value of x
11. (Original post by unamed)
thank you! It just gives me something to go over, I find C3 worryingly easy.
Meh, maths exams are worryingly repetitive when you do a few papers
12. (Original post by milliondollarcorpse)
Meh, maths exams are worryingly repetitive when you do a few papers
that 07 paper was the most different one I've seen. It was not a nice paper to do. (so much trig!) But the June one was quite nice.
My conclusion: The June papers are easier than the January ones. Or, a difficult paper always follows an easy one and vice-versa. (although neither conclusion is good for us , that said, I do better on the harder papers as I'm less likely to make stupid mistakes. )
13. (Original post by unamed)
that 07 paper was the most different one I've seen. It was not a nice paper to do. (so much trig!) But the June one was quite nice.
My conclusion: The June papers are easier than the January ones. Or, a difficult paper always follows an easy one and vice-versa. (although neither conclusion is good for us , that said, I do better on the harder papers as I'm less likely to make stupid mistakes. )
Yeah, I really wouldn't like to have a paper like last summer. 67/75 for an A?! I could probably get that by losing 8 marks through stupid mistakes on a bad day, which would mean I get 80 UMS. I really want as close to 100 as possible!

I'm hoping for a paper with lots of trig in It's actually my favorite part of C3, and it usually means lower grade boundaries!
14. (Original post by milliondollarcorpse)
Yeah, I really wouldn't like to have a paper like last summer. 67/75 for an A?! I could probably get that by losing 8 marks through stupid mistakes on a bad day, which would mean I get 80 UMS. I really want as close to 100 as possible!

I'm hoping for a paper with lots of trig in It's actually my favorite part of C3, and it usually means lower grade boundaries!
How did you do in C1/2 last year? Did you do M1? < I'm curious.
Hehe. But, if it is very easy, you'd finish earlier which would mean more time to go through it!

I love proving trig equations and differentiation. I hate graphs,especially all the inverse trig graphs and the cosec/sec/cot ones..
which reminds me, do we draw in pencil or pen? (I always forget with edexcel's weird policies).
15. (Original post by Marisa_Grace)
Hi Just wondered if anyone could help me in identifying what the background music is on this website:

I was researching him for my art homework and I quite liked the piece playing. If anyone knows, I'd be grateful

Thanks.
There is no background music on that site...
16. Uh-ohh, a week today
I'm going to do some major C3 revision this morning...
17. This was the last question in the Jan 07 paper and i don't know how to do it.

8i) Prove that sec^2x-Cosec^2x = Tan^2x-cot^2x.
I did this part.

ii) Given that y=arccosx.
a) express arcsinx in terms of y.
b) Hence evaluate acrcosx + arcsinx. Give your answer in terms of π (pi).

Got stuck on part ii). Help, please!
18. Sorry BPat, i got stuck on that question, too. So i'm waiting for my teacher to help me tomorrow, I don't understand the markscheme

This was a question on Solomon Paper F, Question 7b:

Find an expression for the inverse function:

f(x) = (3x+2)/(x-1)

I've got up to

y(x-1) = 3x+2

but then the next line on the markscheme says:

x(y-3) = y+2

I don't understand the link between the last two equations Could anybody help, please?
19. (Original post by unamed)
How did you do in C1/2 last year? Did you do M1? < I'm curious.
Hehe. But, if it is very easy, you'd finish earlier which would mean more time to go through it!

I love proving trig equations and differentiation. I hate graphs,especially all the inverse trig graphs and the cosec/sec/cot ones..
which reminds me, do we draw in pencil or pen? (I always forget with edexcel's weird policies).
98 and 95 respectively you? Yeah I hate those graphs too, as well as the graphs arcsinx, arcosx, arctanx etc.

I'm pretty sure we have to use pens throughout the exam, although someone might have to clarify that?

(Original post by BPat)
This was the last question in the Jan 07 paper and i don't know how to do it.

8i) Prove that sec^2x-Cosec^2x = Tan^2x-cot^2x.
I did this part.

ii) Given that y=arccosx.
a) express arcsinx in terms of y.
b) Hence evaluate acrcosx + arcsinx. Give your answer in terms of π (pi).

Got stuck on part ii). Help, please!
Spoiler:
Show

*

Now using the identity:

< answer to the first part

Therefore

*That will suffice for the answer to the first part too.
20. (Original post by TwirlGirl)
Sorry BPat, i got stuck on that question, too. So i'm waiting for my teacher to help me tomorrow, I don't understand the markscheme

This was a question on Solomon Paper F, Question 7b:

Find an expression for the inverse function:

f(x) = (3x+2)/(x-1)

I've got up to

y(x-1) = 3x+2

but then the next line on the markscheme says:

x(y-3) = y+2

I don't understand the link between the last two equations Could anybody help, please?
Expand the brackets on the LHS:

yx-y=3x+2

Move all the x's to the left and everything else on the right:
yx-3x=y+2

Factorise x and that's the next step on the mark scheme

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