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Edexcel A2 C4 Mathematics June 2015 - Official Thread

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Reply 740
Original post by physicsmaths
Not often. But edexcel love surprising people so I would learn them



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You must have been watching hitlers reaction to the papers on YouTube.
is there a lot of error carried forward marks for c4?
Anyone know of any techniques to check if your partial fraction is correct?
Original post by Efemena15
Anyone know of any techniques to check if your partial fraction is correct?


Substitute in a value of x into the original form and your partial fractions form. I normally use 7. If they give the same answer you're almost certainly right.
Original post by Efemena15
Anyone know of any techniques to check if your partial fraction is correct?


Plug numbers in your calculator for x and see if you get the same value.
Original post by Krollo
Substitute in a value of x into the original form and your partial fractions form. I normally use 7. If they give the same answer you're almost certainly right.


Why 7? Lol


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Original post by physicsmaths


Small enough so the numbers involved don't get ungainly; large enough so the chance of getting two equal outputs by accident is negligible. :tongue:
5. Relative to a fixed origin O, the vector equations of the two lines l1 and l2 are l1: r = 9i + 2j + 4k + t(–8i 3j + 5k), and l2: r = –16i + aj + 10k + s(i 4j + 9k), where a is a constant. The two lines intersect at the point A.
(a) Find the value of a. (6)
(b) Find the position vector of the point A. (1)
(c) Prove that the acute angle between l1 and l2 is 60°.
Point B lies on l1 and point C lies on l2. The triangle ABC is equilateral with sides of length 14Ö2.
(d) Find one of the possible position vectors for the point B and the corresponding position vector for the point C

parts a,b,c no problemo. Part D slightly confused although i can do part of it just not sure.
a) -3
b) -15i,-7j+19k
c)show that,

Please help!
Reply 749
Does anybody have tips for parametric into a Cartesian. What do you guys look out for, I seem to be quite weak at it :/


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Original post by lam12
Does anybody have tips for parametric into a Cartesian. What do you guys look out for, I seem to be quite weak at it :/


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Look out for the trig identities


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ImageUploadedByStudent Room1433286268.598854.jpgImageUploadedByStudent Room1433286298.984606.jpgImageUploadedByStudent Room1433286316.203074.jpgImageUploadedByStudent Room1433286333.104038.jpg

Can someone explain why I keep getting the wrong coordinates for d even though my method is the same?!!!


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Original post by Medicjug
ImageUploadedByStudent Room1433286268.598854.jpgImageUploadedByStudent Room1433286298.984606.jpgImageUploadedByStudent Room1433286316.203074.jpgImageUploadedByStudent Room1433286333.104038.jpg

Can someone explain why I keep getting the wrong coordinates for d even though my method is the same?!!!


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Found it was a silly mistake forgot to change sign 🙈


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hey guys

haha i feel like i'm spamming up this page :redface:

quick question: how do you solve cotx=0 I was told by my teacher that you can't solve this but in some of the solomon papers they solve them so very confused right now
Reply 754
Original post by Medicjug
hey guys

haha i feel like i'm spamming up this page :redface:

quick question: how do you solve cotx=0 I was told by my teacher that you can't solve this but in some of the solomon papers they solve them so very confused right now


cotx = 0 implies tanx =
which implies x = +- π/2 +-
Original post by TeeEm
cotx = 0 implies tanx =
which implies x = +- π/2 +-


You dont need he plus or minuses there just let n take positive and negative values 😉


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Reply 756
Original post by physicsmaths
You dont need he plus or minuses there just let n take positive and negative values 😉


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it depends how you define n
Original post by Medicjug
hey guys

haha i feel like i'm spamming up this page :redface:

quick question: how do you solve cotx=0 I was told by my teacher that you can't solve this but in some of the solomon papers they solve them so very confused right now


Or write is as cosx over sinx which would mean cosx is zero

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Reply 758
If you have 3 lns, which order do you add/divide them? Eg. 2ln|2x+1| - 3ln|x+1| + ln|x+3|

Edit: Would it be

ln(2x+1)2(x+3)(x+1)3\ln | \frac{(2x+1)^2 (x+3)}{(x+1)^3} |
(edited 8 years ago)
Original post by Cosmi
If you have 3 lns, which order do you add/divide them? Eg. 2ln|2x+1| - 3ln|x+1| + ln|x+3|

Edit: Would it be

ln(2x+1)2(x+3)(x+1)3\ln | \frac{(2x+1)^2 (x+3)}{(x+1)^3} |


Yep

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