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# Edexcel FP3 - 27th June, 2016 watch

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1. (Original post by oinkk)
It's in a book called "Further Pure Mathematics" and was written around the time of the Stone Age.

This actual question is from 1976.

https://www.amazon.co.uk/gp/aw/d/085...7JL&ref=plSrch
I don't know if it should have but this reply made me laugh out loud.

But yeah, I don't think that will come up in the edexcel spec. Despite that being said, its quite similar to Major-fury 's post. When he,hopefully, posts a solution to his post we can try to derive the method for this one!
2. (Original post by Inges)
Where did you find this???
Start on the right-hand side. It's similar to question 59 RE1.
3. (Original post by oinkk)
Attachment 556903

Thoughts on this one? No idea where to start! I was thinking using the sin A - sin B formula that we never use in C3.
Using that formula got me to the answer so try it
4. (Original post by Major-fury)
from the question we are told plane 1 has vector equation r.(3,-4,2)=5 and that plane 2 has vector equation r=lambda(2,1,5) + mu(1,-1,-2) -- we can assume from plane 2 that the position vector is (0,0,0) so r=(0,0,0) + lambda(2,15) + mu(1,-1,-2).

Then we want the plane 2 in the form r.n=p.
we then cross multiply (2,1,5) and (1,-1,-2) to give us (3,9,-3)
then r.(3,9,-3)=(0,0,0).(3,9,-3) = 0
r can then be written as r.(1.3,-1)=0 (dividing by 3)

now we have 2 equations r.(1,3,-1)=0 and r.(3,-4,2)=5
which can be written as x+3y-z=0 , 3x-4y+2z=5.
in the mark scheme they had let x=0 which gives us 2 simultaneous equations
3y-z=0, 4y+2z=5
you then solve these for the position vector of the 2 planes
and cross multiply (1,3,-1) and (3,-4,2) for the direction vector.
This may seem complicated due to the amount written but it's fairly simple
Ah I see! Thanks so much for clearing this up!

How do we know that a point on the line exists where x=0?
5. can someone explain june 2015 8 b) using pythagoras https://3a14597dd5c7aa2363f067571766...%20Edexcel.pdf
6. (Original post by AmarPatel98)
Ah I see! Thanks so much for clearing this up!

How do we know that a point on the line exists where x=0?
at first we don't but later on when we solve the simultaneous equations if we were given a result like 0=0 we would know that the answer is wrong. for these types of question we can always let x,y or z =0 and then proceed to solve simultaneous equations
7. (Original post by milogillot)
can someone explain june 2015 8 b) using pythagoras https://3a14597dd5c7aa2363f067571766...%20Edexcel.pdf
if you refer back to the formula booklet, you'll see what the general point is. in this case (2cos(theta),sin(theta)). you can then just find the distance pf1 and pf2 and then it'll cancel down to 4.
8. (Original post by oinkk)
Attachment 556903

Thoughts on this one? No idea where to start! I was thinking using the sin A - sin B formula that we never use in C3.
for this question i let sin(2ntheta) = sin((2n-2)theta + 2theta) and then used trig identities and such to cancel it down.

i used the answer we were supposed to find In-1 -- led me to believe this would be a good approach as In-1 = sin ((2n-2)theta)/sin (theta)
9. (Original post by Major-fury)
at first we don't but later on when we solve the simultaneous equations if we were given a result like 0=0 we would know that the answer is wrong. for these types of question we can always let x,y or z =0 and then proceed to solve simultaneous equations
It must be possible for the line to now be over the origin surely? So will this always work
10. (Original post by AmarPatel98)
It must be possible for the line to now be over the origin surely? So will this always work
unless you're really unlucky it should work all the time but just to be safe you could let y=0 or z=0 and solve for those
11. (Original post by Major-fury)
no problem man
can you explain the reduction question for me pls
12. (Original post by anndz3007)
can you explain the reduction question for me pls
could you link me which reduction question?
13. (Original post by Major-fury)
could you link me which reduction question?
is it the one I posted or the one posted
14. (Original post by Major-fury)
could you link me which reduction question?
the sinntheta one that you t asked, i just went round and round with cos and sin :'(
15. (Original post by anndz3007)
the sinntheta one that you t asked, i just went round and round with cos and sin :'(
from the question it talks about In+2. from this we deduce that we'll need sin((n+2)x)
so I let
sin(nx) = sin((n+2)x-2x)
then i proceeded to just expand that out so sin((n+2)x)cos(2x)-cos((n+2)x)sin(x)
and then yeh just trig from then onwards pretty much
16. could someone post some difficult vector and other questions for me? I want to test myself ;P
17. (Original post by Major-fury)
from the question it talks about In+2. from this we deduce that we'll need sin((n+2)x)
so I let
sin(nx) = sin((n+2)x-2x)
then i proceeded to just expand that out so sin((n+2)x)cos(2x)-cos((n+2)x)sin(x)
and then yeh just trig from then onwards pretty much
thanks, i just forgot the 2 in the 1-2sin^2theta, that's why it didnt work, finally mastered this kind of question lol
18. (Original post by 13 1 20 8 42)
Using that formula got me to the answer so try it
Hm, I actually have no idea what to do. I looked at the final result that we need to show, and figured I'd need to use that formula at some point. But I really have no idea how to progress with it.

Are you able to share a worked solution?
19. (Original post by oinkk)
Hm, I actually have no idea what to do. I looked at the final result that we need to show, and figured I'd need to use that formula at some point. But I really have no idea how to progress with it.

Are you able to share a worked solution?
It may well not be optimal, don't have much practice on these questions.

I only had pencil and you can't see a lot of it but I hope what you can see helps..

20. Anyone know where I can go from here? :/

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