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# The Edexcel C4 (21/06/12 - PM) Revision Thread Tweet

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IMPORTANT: You must wait until midnight (morning exams)/4.30AM (afternoon exams) to discuss Edexcel exams and until 1pm/6pm the following day for STEP and IB exams. Please read before posting, including for rules for practical and oral exams. 28-04-2013
1. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by mld)
I agree, Integration is doing in my head!!!

Supposedly we finished the course today, now it's revision - or rather in my case learning it all from scratch.

C4
Maybe you should take some of your own advice? Have you never read "The Power of Positive Thinking"? I haven't, but everything you need is in the title!
2. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by grazie)
Maybe you should take some of your own advice? Have you never read "The Power of Positive Thinking"? I haven't, but everything you need is in the title!
Thanks grazie. Good idea. I've still got time to do all the work.
3. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
Does anyone have a link to the solomon papers?
4. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
4 weeks or so to the exam!
My penultimate exam.

Does anyone have any tips to do rate of change and vectors questions?
5. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
Hey can someone pls show me what the grade boundaries are for 70 Ums and 80 Ums. thanks
6. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
The diagram shows the curve C with parametric equations
x=asin2t, y=acost, 0 ≤ t ≤ 1/2pi

where a is a positive constant. The point P lies on C and has coordinates (3/4a, 1/2a)

(b) Find an equation of the tangent to C at P.

(c) Show that a cartesian equation of C is y2=a2−ax.

The shaded region is bounded by C, the tangent at P and the x-axis. This shaded region is rotated through 2π radians about the x-axis to form a solid of revolution.

(d) Use calculus to calculate the volume of the solid revolution formed, giving your answer in the form kπa3, where k is an exact fraction

i got a, b and c but d is death
can anyone help me out?
7. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by chickpe)
The diagram shows the curve C with parametric equations
x=asin2t, y=acost, 0 ≤ t ≤ 1/2pi

where a is a positive constant. The point P lies on C and has coordinates (3/4a, 1/2a)

(b) Find an equation of the tangent to C at P.

(c) Show that a cartesian equation of C is y2=a2−ax.

The shaded region is bounded by C, the tangent at P and the x-axis. This shaded region is rotated through 2π radians about the x-axis to form a solid of revolution.

(d) Use calculus to calculate the volume of the solid revolution formed, giving your answer in the form kπa3, where k is an exact fraction

i got a, b and c but d is death
can anyone help me out?
Not sure why you're struggling as you've worked out most of what you need earlier in the question. Do you remember how to calculate volumes of revolution?

Work out the limits and you're sorted. BTW, what's the source of the question? It's helpeful for those following the thread.
8. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by Dan4444)
Does anyone have a link to the solomon papers?
http://www.sci2.co.uk/maths.html. Enjoy

BTW, some of the Edexcel question papers on this site are not the final versions and there are a few errors (which would have been there when set!!!). Get the latest versions from the Edexcel website.
Last edited by grazie; 26-05-2012 at 19:13. Reason: Inportant info
9. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
guys i dont understand why, for the answer to question 3c on exercise 6c (integration). is -1/8cos(8x) + 1/2cos(2x) + c

why is it positive 2x and not -2x.
10. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by sukhys)
guys i dont understand why, for the answer to question 3c on exercise 6c (integration). is -1/8cos(8x) + 1/2cos(2x) + c

why is it positive 2x and not -2x.
Look at example c on the page before. Remember sin integrates to -cos.
11. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by NutterFrutter)
Look at example c on the page before. Remember sin integrates to -cos.
i understand that sin integrates to -cos. i dont understand the formulae for difference of sines or cosines which is

2sinAcosB = sin(A+B) + sin(A-B)

A=3x
B=5x

sub them in

2sin3xcos5x = sin(3x+5x) + sin(3x-5x)
2sin3xcos5x = sin8x + sin(-2x)
they got 2x not -2x WHY
12. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
C3 is ****ing easy. Did a past paper after 4 months of no work and got 74/75, I lost one mark on a silly mistake when transforming graphs.

C4 is alright also, I scored 73/75 in my class mock like a don, barely revised too... probably going to do a C4 past paper today, aiming for 100 percent. Wish me luck people!

13. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by sukhys)
2sin3xcos5x = sin(3x+5x) + sin(3x-5x)
2sin3xcos5x = sin8x + sin(-2x)
they got 2x not -2x WHY
Brother, think carefuly! If I hinted as to why I would just give it away. If you can't spot it now, I recommend coming back to the problem tomorrow. That's the most effective way you'll learn, 'self-induced' learning so to speak.
14. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by sukhys)
i understand that sin integrates to -cos. i dont understand the formulae for difference of sines or cosines which is

2sinAcosB = sin(A+B) + sin(A-B)

A=3x
B=5x

sub them in

2sin3xcos5x = sin(3x+5x) + sin(3x-5x)
2sin3xcos5x = sin8x + sin(-2x)
they got 2x not -2x WHY
sin(-x) = -sinx

possibly?
15. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by Ilyas)
Brother, think carefuly! If I hinted as to why I would just give it away. If you can't spot it now, I recommend coming back to the problem tomorrow. That's the most effective way you'll learn, 'self-induced' learning so to speak.
bro, i have no idea why its positive please give me a hint. the only thing i can think of is u cant have a negative angle?
16. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
How does it work to get an A*? I heard that you only need an A overall for EVERY module for maths apart from C3 and C4 where you need 180 UMS across the two for an A*. Is this true?
17. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by sukhys)
i understand that sin integrates to -cos. i dont understand the formulae for difference of sines or cosines which is

2sinAcosB = sin(A+B) + sin(A-B)

A=3x
B=5x

sub them in

2sin3xcos5x = sin(3x+5x) + sin(3x-5x)
2sin3xcos5x = sin8x + sin(-2x)
they got 2x not -2x WHY
Don't know the full question, but I suspect there's a double negative somewhere in the question. sin(-2x)=-sin(2x) so with the double negative you'd have -(-sin(2x)) = sin(2x).

Just a shot in the dark.

__________________

(Original post by sukhys)
the only thing i can think of is u cant have a negative angle?
You can. Angles are sort of like vectors (difference is that angles are restricted to one axial direction, vectors are not). They indicate how far in a certain direction to go, so if it was negative, you'd just go the other way.
Last edited by F1Addict; 26-05-2012 at 18:56.
18. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by NutterFrutter)
sin(-x) = -sinx

possibly?
19. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by KamilS)
How does it work to get an A*? I heard that you only need an A overall for EVERY module for maths apart from C3 and C4 where you need 180 UMS across the two for an A*. Is this true?
no, you need 480 ums and of those 480 ums, 180 MUST come from c3 and c4.
20. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
can anyone confirm that the answer to question 2a on exercise 6D is wrong in the back of the book and the CD solution bank.
and also question 2d answer is wrong in the book and CD solution bank. if these are NOT wrong can some1 please explain how they got that answer.
Last edited by sukhys; 26-05-2012 at 22:56.
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