C3 Jan 2012 Edexcel - Post exam discussion - Solutions and paper in first post

I messed up composite functions...of all the things!! Aaaah. Grrr. I think my grade us gonna depend on method marks seeing as I seem to have an incabability to get final answers correct...

Oh and also - no Rsin/Rcos thing! I like those questions... :frown:

Now I'm just wondering what I was thinking getting 8c correct but only half answering a and b. grrr.

(edited 12 years ago)

Reply 101

Vocker

I had the stupidest mistakes ever!!! Damn I'm ****ing pissed here lol!

But I got a question, if the way was right, but the answer was wrong (for example for the last question, I had 7pi/12, but the way the whole solution was right) how many marks would I lose?

Reply 102

Mr Einstein

14

Ran out of time and made a stupid mistake for the 7 marker on the gradient! fuuuuuuuuuuuuuu.
Otherwise I did pretty well. Still pissed though.

Reply 103

Dan12

Original post by Xarren

Hi, thanks for the answers.

I'm a little bit confused about where I've gone wrong in question 6D:

I went for

(1/2)(3+sin(x/2)-2x)=f(x)

f(1.90775) = 8.17x10-5 > 0

f(1.90785) = -3.83x10-6 < 0

What did I do wrong? Did I do anything wrong? Bit confused.

Would be a shame to get that wrong - I got every other question fully correct, and spent an hour during the exam staring at the ceiling.

If this is wrong - How many marks do you recon I would have lost?

If you mean (1/2)(3+sin(x/2)) -x=f(x) then that's what I got. There was a similar question in june 2006 and you use the simplified version

Reply 104

bbhhuu

For question 7b..find the inverse::: i got 1+x/2x ? is that right?

Reply 105

Mr.cool

1

Original post by bbhhuu

For question 7b..find the inverse::: i got 1+x/2x ? is that right?

yes.

Reply 106

bbhhuu

And for question 4 i did every thing right however i did the differentiation wrong there for i got the gradient wrong how ever i did everything in steps how many marks would i get for that ?

Reply 107

Kirya

6

Think I've got 73/75! Could kick myself for not writing the time as 12:28 and confusing domain with range. It's so easy to make silly mistakes.
It it just me, or did this paper seem much harder than past papers? I took over an hour to do it so didn't have a great deal of time to check it. I normally finish practice papers in around 30 mins. I understand I was stressed, but it did seem harder than I expected it would be.

Reply 108

F1's Finest

21

so annoyed, i screwed up the normal equation question and did the triangle method approach but failed that epically. so annoyed, might have to retake to get an A* now....... reckon i got 66

i feel like punching my pc screen so hard

(edited 12 years ago)

Reply 109

F1's Finest

21

i was trying to get rid of the cos squared bit in the normal question arghhh

Reply 110

bbhhuu

I have done mistakes while doing Q4 when differentiation does that mean i lost all the 7 marks of only 2 or 3 marks?

Reply 111

Jukeboxing

8

Booyah!, 74/75. Please edexcel... 100UMS.

That domain question, grrrrr.

Reply 112

F1's Finest

21

what do you think the grade boundaries for an A will be??

i think i got 66 but im gonna have to retake it to get full ums

What UMS for B?

What if you put the domain, as infinity>f-1x>0 would you get the mark as its the same as f-1x>0, and to prove the tan equation, i put times by secA and secB, got the same answer, would I get the marks, overall decent paper but I had to look at the tan question for ages till I got it.

Reply 115

Alpha5

2

How many marks will I lose for the last one, as I only got 1 solution? For the 10 marker, how many marks do I lose for only getting 3 correct solutions? I think it's 2 and 3 respectively, but what do you guys thinks. Thanks.

(edited 12 years ago)

Reply 116

exam2k10

9

Original post by battsa

For the normal to the curve, i got the correct x coordinate, the right dy/dx in terms of y but somehow worked the gradient out as -1/2 not -8. After that i made an equation using that gradient. How many marks will i have lost?

Got everything else right except the domain, i didn't know what was going on :P

Same. I managed to get my gradient as -1/2 :frown:

. Hopefully, we lose at least one or two marks :crossedf:

Reply 117

Charlesworth

1

Original post by exam2k10

Same. I managed to get my gradient as -1/2 :frown:

. Hopefully, we lose at least one or two marks :crossedf:

Glad I am not the only one who got -1/2 as well :redface:

Hopefully we will get a lot of method marks!

Reply 118

interpolation

Thanks for the model answers arsey :biggrin:

For the 10 mark trig question, i think i remember giving answers to 2 decimal places(force of habit) and i gave 6 solutions, 2 were out of the range of course. how many marks am i likely to lose here?

Reply 119

fudgesundae

16

Original post by Xarren

Hi, thanks for the answers.

I'm a little bit confused about where I've gone wrong in question 6D:

I went for

(1/2)(3+sin(x/2)-2x)=f(x)

f(1.90775) = 8.17x10-5 > 0

f(1.90785) = -3.83x10-6 < 0

What did I do wrong? Did I do anything wrong? Bit confused.

Would be a shame to get that wrong - I got every other question fully correct, and spent an hour during the exam staring at the ceiling.

If this is wrong - How many marks do you recon I would have lost?

You've subbed into the wrong equation. There wasn't a 1/2 in there was there? I thought it was just subbed into:

2x - 3 - 2sin(0.5x)

You will most likely get 1 out of 3. Usually with these questions, you get one mark for each answer and a mark for talking about a sign change.

So you won't get the first mark for f(1.90775)

or the second for f(1.90785).

But if you still went on to talk about there being a sign change you should get the mark fir that.

C3 Jan 2012 Edexcel - Post exam discussion - Solutions and paper in first post

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