C3 Jan 11 Edexcel - Solutions and Paper in the first post (Now On) + TIPS

So is there no generic fool-proof way of transformations, or do we just hope for the best?

Also, I seem to be showing my method differently to the markscheme, but would I lose marks if I still get to the correct answer? For example, I simplify things in a different order to what they do, but I'm still showing a page worth of method and getting the right answer =\ .

Lastly, do you have any tips on getting the range for composite functions? I keep losing marks here as I don't know what to do all of the time =\ .

You shouldn't lose marks for different working.. I think the examiners who mark maths exams know a fair bit of maths themselves, so I think as long as you've done the right thing then you shouldn't.

Reply 581

JH-QC

1

Hi sorry if this has already been asked; can someone please explain to me how they got one of the answers in Q5d in the June 2010 paper... I have the x values for the turning points (7/2 and 1), but when I sub x=7/2 back into dy/dx I keep getting 0 instead of 9e^-7/2.... I dont know how they get that as mine comes out to 9e^-7/2 - 9e^-7/2 so that equals 0...? PLEASE HELP

EDIT: Never mind I figured it out :smile:

substituted it back into original equation instead

(edited 13 years ago)

Reply 582

Arsey

OP

10

Original post by Darthdevidem

Thanks!!

And I'm doing the specimen C3 paper from here (its on page 32)

http://www.edexcel.com/migrationdocuments/GCE%20Curriculum%202000/184697_GCE_Pure_Maths_C1_C4_Specimen_Paper_MkScheme.pdf

The paper is pretty hard, what would you say the grade boundaries would have been if it had been a real paper?

quite low it was a tough one; 56 for 80ums maybe

Reply 583

Arsey

OP

10

Original post by Soppe

hey for the chapter 7 stuff.. i.e double angle formula's or factor formula's... do we have to learn the proofs?

i mean i know the proof for sin squared plus cos squared = 1.... but i meant the rest... need to know the proofs?

thx

yes you need to know them

Reply 584

Andy Ftw

11

Original post by JH-QC

Hi sorry if this has already been asked; can someone please explain to me how they got one of the answers in Q5d in the June 2010 paper... I have the x values for the turning points (7/2 and 1), but when I sub x=7/2 back into dy/dx I keep getting 0 instead of 9e^-7/2.... I dont know how they get that as mine comes out to 9e^-7/2 - 9e^-7/2 so that equals 0...? PLEASE HELP

You're meant to put x=7/2 & x - 1 into the original equation, y = (2x^2-5x+2) e^-x, to get the y co-ords.

By subbing them into dy/dx, you're finding the value of the gradient (not the y co-ord), and you know value for dy/dx = 0, cause these are turning points so the gradiant must be zero! :wink:

Reply 585

anshul95

11

Original post by Anita B. Studin

For the specimen paper q 6b) will I get marks if i say e^-(0.1t) tends towards 0, so T has to be greater than 20degrees? Or is that completely wrong?

Sorry, I know I've asked you a lot of questions tonight :colondollar:

that would be fine. That basically what the mark scheme says but without using limit language. I said the same thing.

Reply 586

ViralRiver

16

Okay thanks.

Another question,

when doing the iteration questions, can I just list x_n = 0.0002 whatever for each one, or do I need to show a method for that?

Also, when I show that a certain root is valid in some interval or whatever, can I leave my answers in standard form? For example

f(0.025) = 4.022 x 10^-3
f(0.035) = -3.20 x 10^-4

There is a change in sign of f(x) between the upper and lower bounds of alpha, and f is continuous, therefore alpha = 0.03 to 2 significant figures.

(Is that a sufficient conclusion?)

Reply 587

Arsey

OP

10

Original post by Anita B. Studin

For the specimen paper q 6b) will I get marks if i say e^-(0.1t) tends towards 0, so T has to be greater than 20degrees? Or is that completely wrong?

Sorry, I know I've asked you a lot of questions tonight :colondollar:

i would put in a -> 0 so 60e^-.1t >0 so ... >20 but yes you are correct

Reply 588

existinggirl

6

Has anyone done the June 2010 paper? I got really confused by an iteration question, it was x n-1 = 1/sin(x) + 1/4 and my answers were completely wrong even though I did exactly what it said. What happened?!

Reply 589

rolo99

Could someone guide me on how to do this question please, thanks :biggrin:

C3.bmp284.1KB

Reply 590

tinofmints

hey guys, do you think there will be questions on the sinP+sinQ=2sin(P+Q/2)cos(P-Q/2) etc

I have done about 6 past papers, I am yet to see one where you are using this formula, they even give you this formula in the pink booklet

Reply 591

chellzey

9

Original post by JH-QC

Hi sorry if this has already been asked; can someone please explain to me how they got one of the answers in Q5d in the June 2010 paper... I have the x values for the turning points (7/2 and 1), but when I sub x=7/2 back into dy/dx I keep getting 0 instead of 9e^-7/2.... I dont know how they get that as mine comes out to 9e^-7/2 - 9e^-7/2 so that equals 0...? PLEASE HELP

EDIT: Never mind I figured it out :smile:

substituted it back into original equation instead

Shouldn't you sub into the orginal equation for C, not dy/dx because you're not looking for the gradient.

Reply 592

username549369

Original post by existinggirl

Has anyone done the June 2010 paper? I got really confused by an iteration question, it was x n-1 = 1/sin(x) + 1/4 and my answers were completely wrong even though I did exactly what it said. What happened?!

Maybe you are using radians instead of degress? Or vice versa

Reply 593

Arsey

OP

10

Original post by ViralRiver

So is there no generic fool-proof way of transformations, or do we just hope for the best?

Also, I seem to be showing my method differently to the markscheme, but would I lose marks if I still get to the correct answer? For example, I simplify things in a different order to what they do, but I'm still showing a page worth of method and getting the right answer =\ .

Lastly, do you have any tips on getting the range for composite functions? I keep losing marks here as I don't know what to do all of the time =\ .

outside the brackets is what you would expect, inside is the opposite.

if in doubt plug values in and plot some points.

check for restrictions in either domain, if so take them into account!

you can either go for a low chart,

find the range of g(x), use that as the domain for f(x) (including any pre-existing domain)

if there are no restrictions, sketching the graph of fg(x) is a good method to find its range.

Reply 594

Firaila

9

Good luck to everyone

I look forward to seeing the solutions... :redface:

Reply 595

God Help Me

2

Original post by Andy Ftw

Try this http://graphsketch.com/ and compare the two :smile:

It really is x^2, just steeper, and that would be more than fine for a sketch if we had to for some reason draw it :P

THANK YOU!! I was looking for this website everywhere. Couldnt' find it
Thanks and good luck for C3

Reply 596

tinofmints

for those of you having trouble with graphy questions and differentiation questions, check out Wolfram Alpha. Very good tool.

Reply 597

F1Addict

12

Original post by existinggirl

Has anyone done the June 2010 paper? I got really confused by an iteration question, it was x n-1 = 1/sin(x) + 1/4 and my answers were completely wrong even though I did exactly what it said. What happened?!

Did you use radians? You might've gone wrong there.

Original post by rohanarora99a

Could someone guide me on how to do this question please, thanks :biggrin:

8)a) Differentiate.
b) x = sin y and y = arcsin x are the same thing. use the answer for and sub the x-value of the coordinate given to get a value for the gradient. Make sure you use radians!
c) Use y - y1 = m(x - x1)
d) Use the equation from part c and work out what x is when y = 0, to show the x-coordinate given.
e) umm, i'd draw a diagram to see the triangle and then go from there. :wink:

Reply 598

anshul95

11

Original post by tinofmints

hey guys, do you think there will be questions on the sinP+sinQ=2sin(P+Q/2)cos(P-Q/2) etc

I have done about 6 past papers, I am yet to see one where you are using this formula, they even give you this formula in the pink booklet