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# Edexcel FP3 June 2015 - Official Thread watch

1. Hi does anyone have any predictions on what the vector question in fp3 will be as I don't have time to learn how to do all of them. Thanks
2. (Original post by gagafacea1)
Did you do 2a, well if you have, do the same with the quadratics in 2b and c.
I did but I don't have the same fraction at the beginning of the answer.
3. How do you integrate coth2x
4. (Original post by nayilgervinho)
I did but I don't have the same fraction at the beginning of the answer.
Now after you do that to the quadratics, use substitution to turn u=x+b , so you end up with a fraction that looks like one of the integrals given in the booklet. Get it?
5. (Original post by Gome44)
Do you mean Flemings left/right hand rule? Grip rule is to do with direction of the field or something
Na I mean grip rule.
The thumb is direction of normal vector. With direction vectors being the turn from a to b ie axb.

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6. (Original post by nayilgervinho)
How do you integrate coth2x
Try using a natural log
7. I can't do this question it looks straightforward, but..

https://3a14597dd5c7aa2363f067571766...%20Edexcel.pdf

q4a
8. (Original post by nayilgervinho)
I can't do this question it looks straightforward, but..

https://3a14597dd5c7aa2363f067571766...%20Edexcel.pdf

q4a
It isn't really, one of the hardest reductions yet (basically the same idea as the regular 2014 paper). Maybe this will help
x^2(x^2 - a)^(k) = x^2(x^2 - a)^(k) - a(x^2 - a)^(k) + a(x^2 - a)^(k)
9. (Original post by 13 1 20 8 42)
It isn't really, one of the hardest reductions yet (basically the same idea as the regular 2014 paper). Maybe this will help
x^2(x^2 - a)^(k) = x^2(x^2 - a)^(k) - a(x^2 - a)^(k) + a(x^2 - a)^(k)
I tried looking at the mark scheme but I don't understand one of their steps can you just do it, it's the only thing in the paper I can't do.
10. (Original post by gagafacea1)
I checked myself multiple times. And yeah I'm pretty sure he never said anything about normalizing the vectors. Also see..
Attachment 433211
What was the whole question , ill try it now

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11. (Original post by nayilgervinho)
I tried looking at the mark scheme but I don't understand one of their steps can you just do it, it's the only thing in the paper I can't do.
I assume you got to having an integral that contains an expression of the form (x^2(3 - x^2)^(n - 1))

x^2(3 - x^2)^(n - 1) = x^2(3 - x^2)^(n - 1) - 3(3 - x^2)^(n - 1) + 3(3 - x^2)^(n - 1)
= (x^2)(3-x^2)^(n - 1) - 3(3 - x^2)^(n - 1) + 3(3 - x^2)^(n - 1)
= (x^2 - 3)(3 - x^2)^(n - 1) + 3(3 - x^2)^(n - 1)
= -(3-x^2)^(n) + 3(3 - x^2)^(n - 1)

And these will give you your In and In-1
(I wasn't looking at the question/was using memory while doing this so if the numbers are in fact not quite the same I apologize)
12. (Original post by 13 1 20 8 42)
I assume you got to having an integral that contains an expression of the form (x^2(3 - x^2)^(n - 1))

x^2(3 - x^2)^(n - 1) = x^2(3 - x^2)^(n - 1) - 3(3 - x^2)^(n - 1) + 3(3 - x^2)^(n - 1)
= (x^2)(3-x^2)^(n - 1) - 3(3 - x^2)^(n - 1) + 3(3 - x^2)^(n - 1)
= (x^2 - 3)(3 - x^2)^(n - 1) + 3(3 - x^2)^(n - 1)
= -(3-x^2)^(n) + 3(3 - x^2)^(n - 1)

And these will give you your In and In-1
(I wasn't looking at the question/was using memory while doing this so if the numbers are in fact not quite the same I apologize)
This paper was harder than june 14 but the grade boundaries were at 65 for an a
13. (Original post by ninjasinpjs)
What was the whole question , ill try it now

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Try ANY question lol, it'll always work. The one I used in the picture was just symmetrical matrix I remember seeing somewhere. The thing is, I don't think you need to normalize the eigenvectors at all!
14. (Original post by gagafacea1)
Guys do you know why we have to normalize the eigenvectors when making the orthogonal matrix (in the process of diagonalization)? Because I've tried numerous times, and I saw on one of the MIT OCW videos the professor NOT doing that, and it still works out the same. Btw I looked at the mark scheme and apparently you HAVE to do that (it says unit eigenvectors), I just don't get why?
if you don't normalise then the final diagonal matrix is multiplied by scalars. So to eliminate that, it is normalised so that value of scalar = 1
15. (Original post by rachu)
if you don't normalise then the final diagonal matrix is multiplied by scalars. So to eliminate that, it is normalised so that value of scalar = 1
Okay but look at this:
(Original post by gagafacea1)
I checked myself multiple times. And yeah I'm pretty sure he never said anything about normalizing the vectors. Also see..Attachment 433211
16. (Original post by rachu)
if you don't normalise then the final diagonal matrix is multiplied by scalars. So to eliminate that, it is normalised so that value of scalar = 1
also this: http://algebra.math.ust.hk/eigen/01_...lecture3.shtml
17. does anyone have anytips for the reduction questions? i always get stuck of them and i really don't want it to mess up my whole paper. any steps that you usually have to follow? or any methods that you commonly use?? really need help on this :s
18. Can some help me with June 10 question 8b

https://2d31ca6ec4f6115572728c3a9168...%20Systems.pdf

I have found X and Y and I subbed them in but I don't get how to simplify for (x^2+y^2)^2
19. June 2013, qu 6 a), I've got this so far, but I don't understand what to do next someone please help
Attached Images
20. june 13 qu 6.pdf (193.5 KB, 48 views)
21. June 2014 ial question 5a
markscheme https://3a14597dd5c7aa2363f067571766...%20Edexcel.pdf

qustion paper https://3a14597dd5c7aa2363f067571766...%20Edexcel.pdf

i don'tt understand where they got the sin^2(theta) in the first line of the markscheme?? split up cos^n(x) to cos(x)cos^n-1(x) and got v=sinx so where did they get sin^2(x) ???

(by x i mean theta, x is just faster to type)

also questions 7a, how to you simplify 720^3/2 x2/9 ???? calc doesn't give exact ans???

and question8d, i don't understand why they have used 2i+j+3k as the point a i thought A in the vector equation of a line is a point on the line, but they have used the direction vector of it???

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