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# Edexcel A2 C4 Mathematics June 2016 - Official Thread watch

1. Hi guys, quick question, when you are solving cos(theta) between to vectors, how do you know which way the vectors are heading if it requires you to find its direction? Say is C was the point of intersection and line 1 has a point A, and line 2 has a point B... Do I move the directions CtoA or AtoC?

Hope that makes sense! pls help
2. (Original post by Lilly1234567890)
guys you know when they ask you to 'use your approximation to estimate an approximate value of blah blah and you have to find X. how do you find x.? for example, ques 4b here:

http://qualifications.pearson.com/co...e_20130618.pdf

hint: you've got to split the surd into two
3. (Original post by theoriginalrpr)
Attachment 555669Can someone help me with this question please! How do u re arrange the diff eqn
Well I assume you've got the partial fraction in (a)?

Then we have 2 - 2/x^2 = 2(x^2 - 1)/x^2.
So by multiplying we get x^2/(x^2-1) dx = 2 dt
Then we can integrate using (a) on the LHS and the RHS is easy
4. Hi guys, quick question, when you are solving cos(theta) between to vectors, how do you know which way the vectors are heading if it requires you to find its direction? Say is C was the point of intersection and line 1 has a point A, and line 2 has a point B... Do I move the directions CtoA or AtoC? Hope that makes sense! pls help
5. (Original post by maruchan)
It was OK. What do you think's going to come up tomorrow? Hopefully it'll be a nice paper! btw how did you find the c3?
i found it hard ngl................ I think this paper will be moderate containing the following:

--> integration by parts
--> differential equation
--> connected rates of change
--> partial fractions involving denom being squared
--> standard parametric equations
--> implicit differentiation
--> standard vectors
--> integration by inspection
6. (Original post by NotoriousS)
Hi guys, quick question, when you are solving cos(theta) between to vectors, how do you know which way the vectors are heading if it requires you to find its direction? Say is C was the point of intersection and line 1 has a point A, and line 2 has a point B... Do I move the directions CtoA or AtoC?

Hope that makes sense! pls help
if i understand what youre asking correctly, it doesnt matter because you just take the modulus of the cos(theta) because most questions ask you to find the acute angle.... hope that helps
7. (Original post by ccharlie97)
Well I assume you've got the partial fraction in (a)?

Then we have 2 - 2/x^2 = 2(x^2 - 1)/x^2.
So by multiplying we get x^2/(x^2-1) dx = 2 dt
Then we can integrate using (a) on the LHS and the RHS is easy
I just moved the 2/x^2 over to the other side :s? Integrated 2/x^2 to get -2/x?
8. (Original post by raman_17)
i found it hard ngl................ I think this paper will be moderate containing the following:

--> integration by parts
--> differential equation
--> connected rates of change
--> partial fractions involving denom being squared
--> standard parametric equations
--> implicit differentiation
--> standard vectors
--> integration by inspection
Hopefully it is as nice as the international C4 paper! Maybe a similar binomial expansion question? btw what other units are you taking? Hope it goes well for you tomorrow
9. Hey, 2015 question 8) b), how you get 2 and 0 as limits?
10. (Original post by maruchan)
Hopefully it is as nice as the international C4 paper! Maybe a similar binomial expansion question? btw what other units are you taking? Hope it goes well for you tomorrow
yup i would like that too

took c2, m1, s1, c3 and tommorow c4
wbu?
11. (Original post by AakashG)
if i understand what youre asking correctly, it doesnt matter because you just take the modulus of the cos(theta) because most questions ask you to find the acute angle.... hope that helps
How about when you're doing dots? Then the positive and negatives surely will make a difference in the answer? E.g. (-2,-3,4) . (6,2,1) is different to (2,3,-4) . (6,2,1) since you'll get a positive answer and a negative giving two different values for theta? sorry
12. (Original post by raman_17)
yup i would like that too

took c2, m1, s1, c3 and tommorow c4
wbu?
c1 c2 c3 c4 fp1 fp2 . How did you find the international C4 Paper? 2016 . What was your hardest paper for C4 ?
13. i dont think i can do this guys.. (
14. (Original post by Don Pedro K.)
I just moved the 2/x^2 over to the other side :s? Integrated 2/x^2 to get -2/x?
You can't do it that way easily, the questions hints at using (a) of course! So you got:

And integrated? Because that doesn't make sense! You can't even solve this like a first order linear differential equation since it isn't of the form:

So solving the differential equation by separation is the way to go here!
15. (Original post by NotoriousS)
Hi guys, quick question, when you are solving cos(theta) between to vectors, how do you know which way the vectors are heading if it requires you to find its direction? Say is C was the point of intersection and line 1 has a point A, and line 2 has a point B... Do I move the directions CtoA or AtoC? Hope that makes sense! pls help
Your vectors have to be going in the same directions e.g

The intersection is C

A lies on l1 and B lies on l2

Calculate vectors CA and CB
16. (Original post by raman_17)
i found it hard ngl................ I think this paper will be moderate containing the following:

--> integration by parts
--> differential equation
--> connected rates of change
--> partial fractions involving denom being squared
--> standard parametric equations
--> implicit differentiation
--> standard vectors
--> integration by inspection
I have a feeling that trapezium rule will come up, it didnt appear in last years paper
17. (Original post by AakashG)
if i understand what youre asking correctly, it doesnt matter because you just take the modulus of the cos(theta) because most questions ask you to find the acute angle.... hope that helps
https://a086a5a2f39bda93734c56a63fab...%20Edexcel.pdf

https://a086a5a2f39bda93734c56a63fab...%20Edexcel.pdf

Question 9.b) here in the mark scheme is saying to make sure directions are shown correctly ?
18. (Original post by NotoriousS)
Hi guys, quick question, when you are solving cos(theta) between to vectors, how do you know which way the vectors are heading if it requires you to find its direction? Say is C was the point of intersection and line 1 has a point A, and line 2 has a point B... Do I move the directions CtoA or AtoC? Hope that makes sense! pls help
It makes sense, when using costheta the direction of the two lines but be of the same direction either both away from the intersection or both towards
19. (Original post by theoriginalrpr)
Attachment 555669Can someone help me with this question please! How do u re arrange the diff eqn
20. (Original post by maruchan)
c1 c2 c3 c4 fp1 fp2 . How did you find the international C4 Paper? 2016 . What was your hardest paper for C4 ?
oh nice how did you find c2?

doing it now

I did all solomon, gold-silver-bronze and some papers here and there, otherwise 2015 was nice

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