Edexcel Maths Jan 08 - C3Watch

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11 years ago
#181
(Original post by Doji)
If you get 2 letters right, do you think you'll get atleast 1 mark?
Depends! Did you guess the answer at being a certain thing or did you have working to justify it! Somehow, it being a 4 mark question i'd say they'll be 2 marks for method and two for the correct letters to numbers. So yeah, if you had two letters and working to justify it you'd definitely get a mark!
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11 years ago
#182
(Original post by Coffe saved my life)
If people honestly believe that was the hardest paper they've asked then i'm convinced they were very wrong.

I'd say this C3 paper was such that there wasn't a particularly stand out superly hard question, but the general difficulty of the questions was higher.

To stick my neck out on the general marks therefore i'd say that the really top marks will be higher than usual but the average will be lower. I'd therefore be surprised if the exam board considered changing grade boundaries or anything...
I agree completely. The papaer was just different than usual. More mathematical and logical thinking required. The paper was a lot different than previous papers, so probably why people found it harder, I think most people obviously practiced past papers, expected a similar exam and were then surprised.
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11 years ago
#183
(Original post by TheBhramaBull)
Wasn't the atom decay one basically like the graph of 1/x when x>0 , I just drew what I remembered a half life graph to be from GCSE Physics.
yes, like this:
http://snhs-plin.barry.edu/cell-biol...b/HALFLIFE.GIF

Graph question - the one with |f(x)|, f(|x|) and 2f(x+1)

Co-ord should be (-6,-8), sorry.
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11 years ago
#184
(Original post by xx-footy-fan-xx)
when u differentiate the equation, u get something like:
2(e^2x)tanx + (e^2x)(secx)^2
take the e^2x out, so u get:

e^2x(2tanx + (secx)^2 = 0 (ignore e^2x coz it will never be zero)

then u know that 1 + (tanx)^2 = (secx)^2

so then u get a quadratic in tanx, then say Y=tanx, solve it, then u get double roots of Y+1 = 0 . so Y = -1 and so tanx = -1
I did something similar, as in I ended up with

2tanx + (secx)^2 = 0
but for some reason what I did something different after that. What I did was:

2sinx/cosx + 1/(cosx)^2 = 0
i then got rid of the (cosx)^2 by multiplying it out so i had
2sinxcosx + 1 = 0
sin2x=-1
2x= -pi/2
x= -pi/4

and i said that if tanx=-1, then x=-pi/4, and since the two answers were the same then the turning point was at tanx=-1
is that method alright do you think?

Btw for the graphes someone please tell what the co-ordinates were? Well actually what i really need is someone to say they weren't A(5,4) and B(-5,-4) cause if they were I will shoot myself. Cause for part c where 2f(x+1) im afraid i made the stupidest mistake ever! I think I had the co-ordinates down as A(10,3) B(-10, -5)...eugh so damn stupid, i mixed up the x and the y co-ordinates - who the hell does that? Thing is at the moment im trying to get another 100%, cause i got that for c2, s1 and for c1 i got 96...but looks like i just threw that away...sigh.
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11 years ago
#185
(Original post by Coffe saved my life)
Depends! Did you guess the answer at being a certain thing or did you have working to justify it! Somehow, it being a 4 mark question i'd say they'll be 2 marks for method and two for the correct letters to numbers. So yeah, if you had two letters and working to justify it you'd definitely get a mark!
Well i did polynomial division, but i clearly ballsed it up as only 2 match, and the other 3 don't lol
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11 years ago
#186
(Original post by Rags241)
I did something similar, as in I ended up with

2tanx + (secx)^2 = 0
but for some reason what I did something different after that. What I did was:

2sinx/cosx + 1/(cosx)^2 = 0
i then got rid of the (cosx)^2 by multiplying it out so i had
2sinxcosx + 1 = 0
sin2x=-1
2x= -pi/2
x= -pi/4

and i said that if tanx=-1, then x=-pi/4, and since the two answers were the same then the turning point was at tanx=-1
is that method alright do you think?

Btw for the graphes someone please tell what the co-ordinates were? Well actually what i really need is someone to say they weren't A(5,4) and B(-5,-4) cause if they were I will shoot myself. Cause for part c where 2f(x+1) im afraid i made the stupidest mistake ever! I think I had the co-ordinates down as A(10,3) B(-10, -5)...eugh so damn stupid, i mixed up the x and the y co-ordinates - who the hell does that? Thing is at the moment im trying to get another 100%, cause i got that for c2, s1 and for c1 i got 96...but looks like i just threw that away...sigh.

i dont know if its wright or not but youll deffinitly get 3/6 or maybe 4/6

btw i did the same as you at first but at last minute i remembered the identity and it all worked out at the end
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11 years ago
#187
(Original post by 1asdf2fdsa)
i dont know if its wright or not but youll deffinitly get 3/6 or maybe 4/6

btw i did the same as you at first but at last minute i remembered the identity and it all worked out at the end
You never know, 100UMS may be 72 (it was in S1 last summer)
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11 years ago
#188
sorry if this has been said before but was the decay graph just a standard half life one?
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11 years ago
#189
I quite liked this paper (a nice break from FP3 ). Having said that, whenever I think a paper goes well I always do badly in it.
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11 years ago
#190
(Original post by jasonm)
sorry if this has been said before but was the decay graph just a standard half life one?
Yes, I think so.
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11 years ago
#191
(Original post by jasonm)
sorry if this has been said before but was the decay graph just a standard half life one?
my one looked like the one in yellow but touching at 1000

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11 years ago
#192
I didnt put the values on the R axis on the half life graph, but got the shape right.
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11 years ago
#193
i thought this paper was difficult....and so did a lot of my college, but that being said...i dont think grade boundries will go down that much. June 07 was 59/75 to get an A so it should be around there.

My take was:

Q1) this question threw me...i didn't really know what to do and spent a ridiculous amount of time one it....i chose to do long division in the end and im sure i got b=0 but i didn't get 0 for e.

Q2) The first part to prove tan x= -1 i didn't get fully, but in the end, i had a quadratic and took out e^2x which left me with (tanx +1) in the bracket so i sed tan x = -1. hehe (hope i got method marks)

b) I could not do this question about the tangent....i got something stupid, i used product rule to differentiate but then couldnt get an equation.

Q3) This question was the easiest on the whole papaer i think...it was iterative and i managed to get all this. Part (a) and (c) were just proving change of sign. (a) you had to use f(1.5) and f(3.5) and then (c) you had to use f(2.545) and f(2.555) i think...or something like that. Not completely sure on what the figures were.

Q4) The graph question was alright, but i made a silly mistake on one of them i think...so i lost 3 marks i think.

Q5) I think i managed to get all of this. (a) R=1000 (b) c=0.000212 (c) R=62.5 so there would be 63 atoms..i rounded up and teacher sed that was right and (d) you just had to draw a graph or 1/x for x>0 and start y axis at 1000.

Q6)I could do the proof mostly, but i messed up the end so i made it up Always a good thing to do...hehe :P I got the values for x at pi/3 and 5pi/3

Q7)i did cos(2x+x) and just expanded out but i didn't get the final answer right i don't think so hopefully got method marks. The second part i got R=5 and a=0.975 or smething like that...can't remember fully and part (c) i don't really remember either....i just put Rsin(x+a)=0 i think.

Q8) parts (a)(b)(c) were all ok, i got x=1/2 for the fg(x) question. I didn't get the find the stationary points though. Were you suppose to do d2y/dx2=0? I used quotient rule to do dy/dx but couldn't do n e thing after that.

Overall..i thought i would be lucky to scrape a B but at this rate, i think i only got like a C or D...looks like i will have to retake in the summer...and i have a feeling ill mess up C4 as all my mates from year above sed that was really hard!
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11 years ago
#194
For the solving trig question i put sec was 1/sin rather than cos (stupid i know)...will i get error carried forward marks?
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11 years ago
#195
u should do if u used the right method throughout the question
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11 years ago
#196
(Original post by cactusjuice)
Being the idiot that I am I got y=x for 2.a and crossed it out. Apart from the first question I thought it was a fairly alright paper. For 7c I got -0.46, although when I checked it with some calculator work it didn't seem to work out entirely correct, did anyone else notice that, or even get the same answer?

On a side note, one of my friends asked our teacher about how to solve questions like that the first one right before the exam. Of course since we're always getting bad luck with exams, it turned up on the very first question and we all thought 'oh crap'. Luckily it got easier.
I got -0.46 too, i thought it was wrong and i didn't finish the question, damn, can someone please tell me if thats the right anwers??

thanks!
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11 years ago
#197
Hi everyone, I was just wondering if the first question on the paper "Iamb" put together was correct..getting a bit worried here lol, but i managed to get
a=2
b=0
c=-1
d=1
e=0
which is what most of u lots got..
James
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11 years ago
#198

Is question one right?
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11 years ago
#199
im pretty sure you are right.
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11 years ago
#200
was it not 2x^4..etc
and divided by x^2 - 1 (x^2 + 0x - 1)
quite confused here, sorry if im mistaken
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