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WJEC C4 17th June 2016 Watch

1. (Original post by Hydeman)
How do you think the 8 marks for part a) of the trig question would be split? Three marks for showing and then five for the rest?
I'd have to say at least 5 for the second part. Was it 8 overall? If so I'd say 3 for proving the statement and 5 for finding values of x.

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2. (Original post by Jack1066)
I found that decent. Some tough ones on there definitely.

I reckon ~55 for an A.

Binomial I got 1/10 for the 2nd bit.

The one with Tan and cot I got 56.9 degrees, 60 something and 1 hundred and something.

For the point P at (1,9) I got 9/2 and 3/2 as values for P

Vector value P I got 10.

The diff equation I messed up part c completely. That was tough.
Yep these are all correct.
I got the same but you factorise it to get x^2(x^2 - 2) + 1 is less than zero so you just have to explain that all the values are positive so it must be greater than zero hence the contradiction

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I did it slightly differently, took the 1 over the other side to -1. Then said how x⁴ and x² are always positive so x was not real ( contradiction)

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4. (Original post by 98matt)
I did it slightly differently, took the 1 over the other side to -1. Then said how x⁴ and x² are always positive so x was not real ( contradiction)

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You're probably more right than what I put. I was sweating by the end of it thinking I ****ed up so wasn't thinking straight.

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Yeah I got the same. Tbh apart from the proof by contradiction question the whole paper was harder than last year I think

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I think that it was possibly the easiest one I've seen...
They give you the hint that you start by squaring, so

(x+1/x)^2<4
x^2+1/x^2+2<4
6. (Original post by IrrationalRoot)
I think that it was possibly the easiest one I've seen...
They give you the hint that you start by squaring, so

(x+1/x)^2<4
x^2+1/x^2+2<4
Yeah I meant that the proof was easier than last years but on the whole it was on par if not harder.

I think they've given up asking hard vector questions now as well.

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Yeah I meant that the proof was easier than last years but on the whole it was on par if not harder.

I think they've given up asking hard vector questions now as well.

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When we did the paper checks and I saw an easy vectors I was like "there is still hope" ahahah

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8. x^4 - 2x^2 + 1 factorises to give

(x^2-1)^2<0 which contradicts that x is real
9. (Original post by 98matt)
When we did the paper checks and I saw an easy vectors I was like "there is still hope" ahahah

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I finished in an hour and literally had about 30 marks yet to answer and panicked so bad. Managed to get everything answered in the end but that vectors question was a dream.

I've realised I ****ed the contradiction up but it's only 2 marks lost.

How do you think C3 went?

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I finished in an hour and literally had about 30 marks yet to answer and panicked so bad. Managed to get everything answered in the end but that vectors question was a dream.

I've realised I ****ed the contradiction up but it's only 2 marks lost.

How do you think C3 went?

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I saw Mathemateg's c3 markscheme. I think I got 68 or 69 /75. I panicked on the circles question and didn't spot it was simple SOHCAHTOA I think c4 went a little better for me today - does anyone know if mathemateg will be doing a markscheme this afternoon or not until Monday?

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The -2 gradient spat out y=0 and x^2 = -4y^3.

You ignored the x value and plugged in y=0 into original equation, that gave you x^4= 16 which is plus/minus 2 so coordinates (-2,0) (2,0)

I think that was correct.

Agreed though, tough paper but hopefully the lower boundaries push my grades up.

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what do you mean spat out?
i put the gradient equal to -2 and rearranged it but couldnt work out how to separate the x and y terms :/
12. (Original post by aehr)
what do you mean spat out?
i put the gradient equal to -2 and rearranged it but couldnt work out how to separate the x and y terms :/
Yeh he's right (I think). One of the terms was the same on both sides and it cancelled. You had to factorise out the 3y in order to separate the terms. I got to 3y=0 but thought that was trivial so didn't plug it in to the original eqn

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13. I got t = 8 years on the differential equations Q but a few of you have said it was 10 :/ how did you get it?
14. (Original post by 98matt)
Agreed ahahaha. I really hope mathemateg's mark scheme is up today

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Agreed
15. (Original post by aehr)
I got t = 8 years on the differential equations Q but a few of you have said it was 10 :/ how did you get it?
I first worked out b= 1.5, I don't think that was necessary though. Then I stuck in (A/4)² = A²/1.5t+1

I divided through by A², did a bit of rearranging and got t=10

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16. (Original post by aehr)
what do you mean spat out?
i put the gradient equal to -2 and rearranged it but couldnt work out how to separate the x and y terms :/
When you rearranged the gradient = -2 you ended up with a few x and y terms which when factorised gave 3y( something else ) = 0 so y=0 was one. The other term had no solutions. Sub in y=0 into the original equation removed all y terms so you could work out x

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17. (Original post by 98matt)
I first worked out b= 1.5, I don't think that was necessary though. Then I stuck in (A/4)² = A²/1.5t+1

I divided through by A², did a bit of rearranging and got t=10

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I fluked that question. It just didn't click but managed to grind out t=10. I took like a whole page going round in circles

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The -2 gradient spat out y=0 and x^2 = -4y^3.

You ignored the x value and plugged in y=0 into original equation, that gave you x^4= 16 which is plus/minus 2 so coordinates (-2,0) (2,0)

I think that was correct.

Agreed though, tough paper but hopefully the lower boundaries push my grades up.

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You certainly would not just 'ignore the x value here'. y=0 is one solution, the other is the one in the bracket, which gave you x^2+4y^2=0 (not what you said) and you don't ignore this either, you have to say that this is not possible unless y=0.
19. (Original post by aehr)
I got t = 8 years on the differential equations Q but a few of you have said it was 10 :/ how did you get it?
Yep 10. You probs just made a mistake in the algebra.
20. Could someone clear up what you had before you substituted b in the differential?

Im glad you found the gradient -2 question so easy. I didnt see how easy it is....

That damn tan factorisation....

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