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# Edexcel C2 20th May 2015 *Official Thread* watch

1. (Original post by Haych97)
part b
you know nb=12
now for the x^2 coefficient
it's equal to n(n-1)/2! (bx)^2
so n^2-n/2 b^2 =70
solve the simultaneous equations
2. (Original post by sharp018)
Guys when do I need to change from degrees to radians mode on my calc? HELP
if the question is about pi, then you do radians. most of the stuff on sectors will be in radians aswell.
3. (Original post by .JC.)
Care to elaborate?
Lool
I found model answers for this paper, it explains the whole question
https://e85afdd1ce02d2224940da7b2c38...by%20Arsey.pdf
4. Guys, if you have a right angled triangle when finding the area do you use: 1/2*b*h or the 1/2*a*b*sinC?
5. (Original post by sharp018)
but if I'm using the equation for example when the angle given is in radians and I want to find the arc length, so the formula is theta x r, do I still need to switch to radians mode?
Yes always use radians, otherwise if you use degrees, the arc length would be enormously big. For example, consider a sector with a radius of 6cm and an angle of 60 degree.

Arc length using degrees would give 360cm, whereas using radians would give 2pi.
6. Can someone explain how you do question 4b)

https://b940eb267c31463d4d23ccfd3105...%20Edexcel.pdf

Explaining it too xxx

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8. (Original post by Olon)
Guys, if you have a right angled triangle when finding the area do you use: 1/2*b*h or the 1/2*a*b*sinC?
BxH/2

1/2ab x sinC is for non right angle triangles

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9. Does anyone has any notes on volume and surface area of shapes? It just so happens to be the only thing I struggle on C2, but the rest are easy -.-
10. Can someone give me some pointers on part b of this question? I'm not sure if it's really simple but my mind's just gone blank, sorry. Also really sorry if someone's posted this already.
11. (Original post by frozo123)
in the formula booklet there are two formulae for binomial expansions

one is in the form ( 1 +x)^n
where the first number has to be 1
so if I had (3+6x)^ 4
I would have to do first of all ( 3(1+2x) ) ^4 then 81 (1 +2x)^4
then you just follow the formula
it's easier than the nCr crap
Thanks, I tend to use a formula with nCr which looks like:

(a)^n + (a)^n-1 x (bx)^r x (nCr)

When I tried using it for questions with an unknown power, it was tough when it came to the nCr part.
12. (Original post by falloutboyyy)

Explaining it too xxx

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Part a make equation of curve eual to equation of line. Then silve similtanouslu

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13. (Original post by .JC.)
Thanks, I tend to use a formula with nCr which looks like:

(a)^n + (a)^n-1 x (bx)^r x (nCr)

When I tried using it for questions with an unknown power, it was tough when it came to the nCr part.
Just use the other one it's easier and you'll have to use it in c4 anyway so you'll be good at it before you even need it
14. I still don't get it even though i've looked at the markscheme Thanks! I'm confused with the sum to infinity part...
Attached Images

15. (Original post by zaini101)
Soo confused?

in some question the geometric sequence power r has been subtracted by minus 1 in other question it remains unchanged.
how do we know when to subtract 1 or leave r with no power?

Help plzzzz
16. (Original post by falloutboyyy)

Explaining it too xxx

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draw a line from B to the x axis you have a triangle

then find the area from the limits A-B and then subtract the triangle which = area of R
17. (Original post by zaini101)
Help plzzzz
Give an example of question.
I find it tricky sometimes usually when there are years involved.

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18. (Original post by falloutboyyy)

Explaining it too xxx

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In june 2011 Q9 there is only one part A) and B) is it that question?
19. (Original post by kkboyk)
Does anyone has any notes on volume and surface area of shapes? It just so happens to be the only thing I struggle on C2, but the rest are easy -.-
Yeah

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20. (Original post by mrnazz00923)
Yeah

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Thanks!!

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