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Official C3 Exam Discussion WJEC - 24/05/13

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This was most of my answers for C3. The may or may not be correct. Would like feedback if anyone else had similar answers. Also, have missed out a few. Didn't have enough time to write them down at the end.

1) Simpson Rule, a) 5.328 b)Didn't understand :/
2) Theta, a) 41.81, 138.19, 194.48, 345.52 b) 210, 330
3) Curve, a) [-3x(Sqaured).y(Squared)] / [x(cubed).2y] b) ii) a=2, b=-4
4) In Terms T, a) 20t(Power 4) b) t=0.3

7) Inequality, b) 2>x<4
8) Alpha = -1.67723
9) Graph was flipped, with co-ordinates (-5,0), (-1,4), (3,0)
10) a) f-1(x) = -2(ln(x-6)-5) b) [7, infinite)
11) a) i) Domain (0, (Pi/4)] b) i) x= 33.84

So, that was some of my answers. Anyone else get similar answers?

Reply 24

Tania2k9

hi, for question 1 i had 5. soemthing and for the second part i had 2.644 and for 2b) i did sine (thi) -0.5 and got 210 and 330 for 3b i partly showed b=-2a i defo got the values of a and b wrong (probs one mark for working out). For 4b i got t=0.3, 6b i got 1.444 or 13/9 for 7b- <= 4 and >=2

Reply 25

Tania2k9

i got everything , except the value of a andb and for x its actually 33.82 :smile:

Reply 26

L'Evil Fish

Original post by GeorgeLow

I got really similar answers!!!!!

1)b) was log.rule

Had to halve your first approximation

Reply 27

username890104

Original post by Tania2k9

i got everything , except the value of a andb and for x its actually 33.82 :smile:

I'm assuming that fg(x) = -0.4 on the scan (it's a bit blurry)? If so, then it's 33.83 (2dp) as the calculator gives 33.83473935...

Reply 28

L'Evil Fish

Original post by Tullia

I'm assuming that fg(x) = -0.4 on the scan (it's a bit blurry)? If so, then it's 33.83 (2dp) as the calculator gives 33.83473935...

Yeah, I got that. I also gave an answer in radians on the side to 2 dp. Is that okay?

Reply 29

Tania2k9

i hope 33.82 is right, on the calculator do e-0.4 then to shift tan of that answer and you get 33.822085

Reply 30

priteshp

I did that answer in radians? Is that wrong??

Reply 31

Lizard cream

I did it in rads as the domain was in terms of pi. :smile:

overall a nice paper. Can't see where I've lost the marks yet. Probably the functions knowing me. :smile:

Reply 32

priteshp

Phewww haha I did my f-1(x) on Q10 as

-2ln(x-6)+10. ?? Is that right bc I just expanded the brackets out :/

Reply 33

username890104

Original post by L'Evil Fish

Yeah, I got that. I also gave an answer in radians on the side to 2 dp. Is that okay?

I would've given it in rads for the reason given above, but I don't think they'll mark you down for having put them both to two decimal places. I expect they'll accept the answer in only degrees as well, but don't take my word as gospel on that.

Reply 34

L'Evil Fish

Original post by Lizard cream

I did it in rads as the domain was in terms of pi. :smile:

overall a nice paper. Can't see where I've lost the marks yet. Probably the functions knowing me. :smile:

I agree! Definitely functions

Reply 35

username890104

Original post by priteshp

Phewww haha I did my f-1(x) on Q10 as

-2ln(x-6)+10. ?? Is that right bc I just expanded the brackets out :/

That'll be fine. Although, I would have wrote it the other way around as it looks easier on the eye.

Reply 36

priteshp

What did ppl have for the fg(x) range??? I got 0,-infinity

Reply 37

username890104

Original post by priteshp

What did ppl have for the fg(x) range??? I got 0,-infinity

That's incorrect, I'm afraid.

What was the answer?

Tricky exam in places, on 7b I lost some marks, I spaced and didn't combine the intervals, should have got something like -4<=x<=-2 or 2<=x<=4 I think. :frown:

Also, for question 4b does it ask for t or for x, I can't remember, I only solved for t so I was wondering if you then have to substitute to find x or was it finished at t?