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

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1. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
can someone help me with solomon paper L
qs 5 - partial fractions- i dont understand why they have multiplied c by (1-x) eventhough the denominator is (1-x)^2 :/

http://www.school-portal.co.uk/Group...urceId=3992069
http://www.school-portal.co.uk/Group...urceId=3992057
2. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by Jack_Smith)
can someone help me with solomon paper L
qs 5 - partial fractions- i dont understand why they have multiplied c by (1-x) eventhough the denominator is (1-x)^2 :/

http://www.school-portal.co.uk/Group...urceId=3992069
http://www.school-portal.co.uk/Group...urceId=3992057
Definitely a mistake there!
3. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by ViralRiver)
Definitely a mistake there!
Great that means the answers for the next question is wrong aswel!
Thanks Mate!
4. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by ezioaudi77)
You are already there. Remember that:

Oh okay! Thanks where did you get that rule from? Do you have any kind of document with all the log rules?
5. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by Jack_Smith)
Oh okay! Thanks where did you get that rule from? Do you have any kind of document with all the log rules?
That comes from the standard . Conversely, you could use the power rule to show: .
6. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
If anyone's taking C3 as well, make sure to take a look at the differential equation from the jan '11 paper. It was definitely one of the more difficult ones I've seen, and when I did it I could have sworn I needed to apply knowledge from C4 for it.
7. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
∫sin 3x cos x dx

what is the integration of this?
8. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by Jack_Smith)
∫sin 3x cos x dx

what is the integration of this?
I've never seen something like that before, but I tried something and it simplifies it to something that can be integrated a lot more easily.

Use the double angle sin formula . Simplify a little bit and then use the cos double angle . After a little bit of simplification you should have:

. Use integral of sums is sum of integrals to split it up in to two integral problems. The first one is not the easiest integral, but you could make a substitution of u = 2x and realise that cos(u) is the derivative of sin(u) which will help with one of those integral inspection methods.
9. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by ViralRiver)
I've never seen something like that before, but I tried something and it simplifies it to something that can be integrated a lot more easily.

Use the double angle sin formula . Simplify a little bit and then use the cos double angle . After a little bit of simplification you should have:

. Use integral of sums is sum of integrals to split it up in to two integral problems. The first one is not the easiest integral, but you could make a substitution of u = 2x and realise that cos(u) is the derivative of sin(u) which will help with one of those integral inspection methods.
Oh okay.. this is a solomon paper questions so its a bit harder!
But can you help me on QS5 Jun 05

For some reason i dont get what they've done on the ms :/
10. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by Jack_Smith)
Oh okay.. this is a solomon paper questions so its a bit harder!
But can you help me on QS5 Jun 05

For some reason i dont get what they've done on the ms :/
The method I outlined isn't the only method, but it's the only one I can think of using C4 methods - so even though it is a long method it does work :P .

You'll need to link to the paper and ms.
11. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by Jack_Smith)
Oh okay.. this is a solomon paper questions so its a bit harder!
But can you help me on QS5 Jun 05

For some reason i dont get what they've done on the ms :/
5a is integration by parts.
12. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by ViralRiver)
The method I outlined isn't the only method, but it's the only one I can think of using C4 methods - so even though it is a long method it does work :P .

You'll need to link to the paper and ms.
http://www.edexcel.com/quals/gce/gce...s/default.aspx
the paper is a word doc!
I know that its integration by parts but i dont get what the ms said :/
13. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by NutterFrutter)
5a is integration by parts.
yep but dont get the ms :/ quite unsure where the 3/2 went?? where the costheta disappeared to
14. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by Jack_Smith)
yep but dont get the ms :/ quite unsure where the 3/2 went?? where the costheta disappeared to
Are we talking about the same question? Question 5 on June 2005?
15. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by NutterFrutter)
Are we talking about the same question? Question 5 on June 2005?
yep!
16. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by Jack_Smith)
yep!
Question 5 does not involved cos or a 3/2. Question 4 does, maybe you're talking about that?

Question 4 is integration by substitution. The 3/2 disappears because your have cos^2(theta) on the bottom but it's to the power 3/2 so overall at the bottom you get cos^3(theta), this is then cancelled with the cos(theta) on top to leave just cos^2(theta) on the bottom.
17. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by NutterFrutter)
Question 5 does not involved cos or a 3/2. Question 4 does, maybe you're talking about that?

Question 4 is integration by substitution. The 3/2 disappears because your have cos^2(theta) on the bottom but it's to the power 3/2 so overall at the bottom you get cos^3(theta), this is then cancelled with the cos(theta) on top to leave just cos^2(theta) on the bottom.
okay i think i meant that question!! Oh okay i get it now thanks!!
18. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
Can anyone help me on this? I hate these types of questions..

The area A of a circle is increasing at a constant rate of 1.5 cm^2s^–1. Find, to 3 significant figures, the rate at which the radius r of the circle is increasing when the area of the circle is 2 cm^2.
19. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
(Original post by -James-)
are there any other log rules we need to know besides the one you just mentioned at the addition, subtraction, power and change of base ?
(Original post by Jack_Smith)
Oh okay! Thanks where did you get that rule from? Do you have any kind of document with all the log rules?
The best place you can find all the log rules we need to know is Edexcel's C2 textbook (follow this link to view it online). It contains only the rules we need to know and also they are well explained. Below is the summary provided and I added the natural logarithm rules

Summary of Exponential and Logarithms

**Remember that .

A function or , where is a constant, is called an exponential.

means that , where is called the base of the logarithm. So means that .

. So, .
. So, .

is sometimes written as .

The laws of logarithms are
. So (the multiplication rule)

. So (the division law)

. So (the power law)

From the power law,
. So

You can solve an equation such as by first taking the logarithms (to the base 10) of each side OR the natural logarithm of both sides. will be

The change in base rule for logarithms can be written as , so .

From the change of base rule, . So

Hope that helps
20. Re: The Edexcel C4 (21/06/12 - PM) Revision Thread
Does anyone have any tips for how to do differential equations? I'm talking about those really worded ones, where you have to show the differential equation/ make one? Can never do them properly! :l
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