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# C4 (Not MEI) - Thursday June 21 2012, PM Tweet

Maths exam discussion - share revision tips in preparation for GCSE, A Level and other maths exams and discuss how they went afterwards.

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1. Re: C4 (Not MEI) - Thursday June 21 2012, PM
(Original post by a10)
how do you get sec^2x -1 ???!
tan^2(x) + 1 = sec^2(x) from c3
2. Re: C4 (Not MEI) - Thursday June 21 2012, PM
(Original post by BillyFord188)
Sin^2x + Cos^2x = 1 Divide throughout by cos^2x, giving:

tan^2x + 1 = sec^2x
omg i feel stupid now hahahaa funny thing is i actually thought about that this is what happens to me all the time the simple stuff that i know i end up forgetting ecause of the exam stress xD hope that doesnt happen tomoro
3. Re: C4 (Not MEI) - Thursday June 21 2012, PM
Well I need 93 in each of the c4 and fp2 papers So it looks like A* is far away from me.. An A grade would be great. I hate vectors!! I pretty much like rates of change cause you can really see the applications of mathematics. Best of luck to everybody- hoping for some easy vectors exercise
4. Re: C4 (Not MEI) - Thursday June 21 2012, PM
(Original post by paullys)
Well I need 93 in each of the c4 and fp2 papers So it looks like A* is far away from me.. An A grade would be great. I hate vectors!! I pretty much like rates of change cause you can really see the applications of mathematics. Best of luck to everybody- hoping for some easy vectors exercise
im thinking of doing Further maths hw is it? i finish my a level maths after c4 exam tomoro :P is fp1 and fp2 nice?
5. Re: C4 (Not MEI) - Thursday June 21 2012, PM
Would someone mind explaining 5 b on jan 10.

Question starts with i) expand (1+x)^(1/3)

Then ii) Hence expand (8+16x)^(1/3)

Then B) State the range of values the expansion in ii is valid? answer is
-0.5<x<0.5 no idea why?!

Or along those line anyway....

Thanks!
6. Re: C4 (Not MEI) - Thursday June 21 2012, PM
(Original post by Ouzo)
Would someone mind explaining 5 b on jan 10.

Question starts with i) expand (1+x)^(1/3)

Then ii) Hence expand (8+16x)^(1/3)

Then B) State the range of values the expansion in ii is valid? answer is
-0.5<x<0.5 no idea why?!

Or along those line anyway....

Thanks!
You can re-write (8+16x)^1/3 as (8(1+2x))^1/3 , so 2(1+2x)^1/3

I believe this is a standard question type.

|2x|<1 for expansion to apply, so |x|<0.5
Last edited by Killjoy-; 20-06-2012 at 23:55.
7. Re: C4 (Not MEI) - Thursday June 21 2012, PM
(Original post by Killjoy-)
You can re-write (8+16x)^1/3 as (8(1+2x))^1/3 , so 2(1+2x)^1/3

I believe this is a standard question type.

|2x|<1 for expansion to apply, so |x|<0.5
Yeah i get how to rearrange it to get 2(1+2x)^1/3. But then why can't x be any value? Am I being really stupid? I don't get it?
8. Isn't it because the series would diverge? |x| or whatever is in the brackets has to be less than one so the series converges

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9. Re: C4 (Not MEI) - Thursday June 21 2012, PM
Good luck everyone
10. (Original post by Ouzo)
Yeah i get how to rearrange it to get 2(1+2x)^1/3. But then why can't x be any value? Am I being really stupid? I don't get it?
For the binomial expansion thingy -1<x<1 (the signs are less than or equal too by the way)
So in your case it would be
-1<2x<1
-0.5<x<0.5

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11. Re: C4 (Not MEI) - Thursday June 21 2012, PM
(Original post by a10)
im thinking of doing Further maths hw is it? i finish my a level maths after c4 exam tomoro :P is fp1 and fp2 nice?
fp1 is pretty simple, like the difficultly of C1 C2. fp2 on the other hand is HARDDD
12. Re: C4 (Not MEI) - Thursday June 21 2012, PM
holy dick that is so good why didn't you post this earlier D:
still, thank you so much!
13. Re: C4 (Not MEI) - Thursday June 21 2012, PM
When do u take figures in front of the integral and what would the answer be different if u didn't or did take figures out in front of the intergral
14. Re: C4 (Not MEI) - Thursday June 21 2012, PM
i have come to terms with the fact the vectors question where you will form traingles is probably beyond me as my diagrams are abysmal.

I can should be able to get my B in C4 but I make so many silly errors(negative numbers, forgetting to do little things) it seems unlikely as my mistakes usually happen at the begging of the question so I lose a lot of the accuracy marks. But I know pretty much all the content its so unfair .
15. @Rsk22 you don't HAVE to take any figured out in front of the integral, but some people find it makes it easier to do so, for example when integrating to find a volume, you can take pi out of the integral. It doesn't make any difference to the answer if you do it correctly! X

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16. Re: C4 (Not MEI) - Thursday June 21 2012, PM
(Original post by Akbar2k7)
i have come to terms with the fact the vectors question where you will form traingles is probably beyond me as my diagrams are abysmal.

I can should be able to get my B in C4 but I make so many silly errors(negative numbers, forgetting to do little things) it seems unlikely as my mistakes usually happen at the begging of the question so I lose a lot of the accuracy marks. But I know pretty much all the content its so unfair .
I make silly mistakes too. I need 79 UMS on my final two modules to get an A... I'm feeling the pressure :/
17. Re: C4 (Not MEI) - Thursday June 21 2012, PM
for vectors questions where you need to find angles, can use use both rad and degrees? does it not really matter unless they say specifically? please help!
18. Re: C4 (Not MEI) - Thursday June 21 2012, PM
(Original post by jahani08)
for vectors questions where you need to find angles, can use use both rad and degrees? does it not really matter unless they say specifically? please help!
Any'll be accepted. Degrees are the most standard for those questions though
19. Re: C4 (Not MEI) - Thursday June 21 2012, PM
(Original post by jahani08)
for vectors questions where you need to find angles, can use use both rad and degrees? does it not really matter unless they say specifically? please help!
you can use either as long as you make it clear which you have done, in general on mark schemes for past paper they have both answers as acceptable i always choose to use degrees but that's just personal preference
20. Re: C4 (Not MEI) - Thursday June 21 2012, PM
Okay for June 10 question 6b I took out a half but they didn't do this in the mark scheme and I got a different answer
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