Edexcel A2 C4 Mathematics June 2016 - Official Thread

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

Reply 3601

AakashG

1

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/content/dam/pdf/A%20Level/Mathematics/2013/Exam%20materials/6666_01R_que_20130618.pdf

hint: you've got to split the surd into two

Reply 3602

ccharlie97

3

Original post by theoriginalrpr

Can 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

Reply 3603

NotoriousS

7

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

Reply 3604

raman_17

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? :wink:

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
:biggrin:

Reply 3605

AakashG

1

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

Reply 3606

Don Pedro K.

9

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?

Reply 3607

maruchan

12

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
:biggrin:

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

Reply 3608

sakuraton

12

Hey, 2015 question 8) b), how you get 2 and 0 as limits?

Reply 3609

raman_17

5

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 :biggrin:

took c2, m1, s1, c3 and tommorow c4 :redface:

wbu?

Reply 3610

NotoriousS

7

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

Reply 3611

maruchan

12

Original post by raman_17

yup i would like that too :biggrin:

took c2, m1, s1, c3 and tommorow c4 :redface:

wbu?

c1 c2 c3 c4 fp1 fp2 . How did you find the international C4 Paper? 2016 . What was your hardest paper for C4 ?

Reply 3612

thuphammm

1

i dont think i can do this guys.. :frown:

(

Reply 3613

ccharlie97

3

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:

2/x^2 + \mathrm d x/\mathrm d t = 2

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:

\mathrm d x/\mathrm d t + p(t)*x = q(t)

So solving the differential equation by separation is the way to go here!

Reply 3614

taysc

2

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

Reply 3615

leestitt

2

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
:biggrin:

I have a feeling that trapezium rule will come up, it didnt appear in last years paper

Reply 3616

NotoriousS

7

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://a086a5a2f39bda93734c56a63fab1d7be0a9ba38.googledrive.com/host/0B1ZiqBksUHNYQXE5T2xiNDBRd2s/Specimen%20(IAL)%20QP%20-%20C34%20Edexcel.pdf

https://a086a5a2f39bda93734c56a63fab1d7be0a9ba38.googledrive.com/host/0B1ZiqBksUHNYQXE5T2xiNDBRd2s/Specimen%20(IAL)%20MS%20-%20C34%20Edexcel.pdf

Question 9.b) here in the mark scheme is saying to make sure directions are shown correctly ?

Reply 3617

Brailey

2

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