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Edexcel C3 June 2016 - Unofficial Mark Scheme

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i'm so confused now was it pi -pi or pi/2 -pi/2 because everyone is saying different things. i thought that it was between -pi and pi but now i'm not sure...

Reply 281

Nooneforyou27

Original post by Linguist131

@veldt127 Is there any chance you can explain / show us working for question 7b)? I thought I got the answer at the time but I seem to remember my answer being different to yours - the question was to solve
3g(x+1) + 1 = 0
with g(x) = arcsinx
if I remember correctly? Thank you - and thanks so much for your answers, they're great! :smile:

It was 3g(x+1)+pi=0

Reply 282

carrm123

Original post by Kay Fearn

Yeah but i just left it as it's exact value, i thought that's what you had to do when it came to stuff with pi :-(

I think I did the same as you, I left it as x=sin(-pi/3) - 1
I think we might lose 1 mark but I'm hoping not seeing as it's technically correct

Reply 283

jj202

Original post by jack_98

do you know for 8b how many marks

It was 6 marks.

Reply 284

Kay Fearn

Original post by jj202

It was 6 marks.

for 8b wasn't the range -pi/2 to pi/2 or something like that. I remember only being able to use two values from the 4 mentioned by OP

Reply 285

Paddycat12

was 5i) tan(4/3) can't remember what i put and for 8b) did people use quadratic equation and get like -4 and 1 before you inverse tan to get the answer

Reply 286

Ayagh

Original post by tigermoth890

Hi I think that is the one where you had 0=e^2x(3sintheta - 4costheta)

Something like that.
Then you end with tantheta = 3/4 or something.

do you remember the question and how you solved it , thank you so much . Because i forgot my final answer

Yay thank u so much but i forgot how i solved it

(edited 7 years ago)

Reply 287

the___jackal

did it specify the normal equation in the form y= ?

Reply 288

jj202

Original post by veldt127

Like I said, if people have the questions I can work through them, I've done working for all the ones I could remember

Q8 b was this: solve the equation 6cot2x + 3tanx = cosec^2x - 1

Reply 289

KinggBubba

Original post by particlestudent

Im sure only the middle two values were allowed for 8B

It was between -ve and +ve pi, though to get full marks I only think you need two solutions, so you should be fine lad

Reply 290

rk_

Original post by Ashleighh37

does anyone know how many marks each questions is worth?

http://www.thestudentroom.co.uk/showthread.php?t=3847081&page=92

Reply 291

samkts

Original post by veldt127

I'm not 100% sure on all of these, but I think most are correct.

Question 1

Spoiler

Question 2

Spoiler

Question 3

Spoiler

Question 4

Spoiler

Question 5

Spoiler

Question 6

Spoiler

Question 7

Spoiler

Question 8

Spoiler

Question 9

Spoiler

PDF with working for 1-4 and 9 : http://www.thestudentroom.co.uk/attachment.php?attachmentid=554155&d=1466508775

isn't your answer for 7 part b outside the range of what x could be? wasn't it between -1 and 1?

Reply 292

veldt127

Original post by jj202

Q8 b was this: solve the equation 6cot2x + 3tanx = cosec^2x - 1

Ah right. You knew acot2x + tanx = cotx from part a

so 3cotx = cosec^2x - 2

cosex^2x = 1 + cot^2x

Then it's a quadratic; cot^2x - 3cotx - 1 = 0
cot x = 3(+/-)sqrt(13) divided by 2

tan x is the reciprocal of that; I'm not entirely sure on the +1/-1/-2 part but it was along those lines.

Reply 293

veldt127

Original post by samkts

isn't your answer for 7 part b outside the range of what x could be? wasn't it between -1 and 1?

It was actually g(x+1) so the range would be lower - move the graph 1 to the left.

Reply 294

Craig1998

The examiner must think I'm on drugs for one of the questions. I misread the limits as -pi/4 to pi/2 for one question, rather than pi/4 to pi/2 (the tan(-3/4) one). So I kept getting two answers and starting over. Did this about 3 times before realising.

Original post by PeterMJP

If you put 2cosec4y but did all working out correct how marks would you lose and what do people think an A will be?

Probably just the 1.

Reply 295

xdaryaxx

What do u think the grade boundaries are

Reply 296

keyadeb

how many mark would i lose if i didn't put the inequalities signs correctly?
I did however get + and - root5

(edited 7 years ago)

Reply 297

Angus09

Original post by jwanjwan

i agree however i dont know about 7 part b, i cant really remember the question but i believe i left it in terms of sin but your answer looks more complete