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# OCR MEI Core 4 (C4 4754/01 and 4754/02) watch

1. (Original post by Sabster)
I did this deifferently:

a = theta

x = cos 2a
= (cosa)^2 - (sina)^2
x^2 = (cosa)^4 + (sina) ^ 4 - 2(sina)^2(cosa)^2

+ 4y2 (4(cosa)^2(sina)^2)

= (cosa)^4 + (sina) ^ 4 + 2(sina)^2(cosa)^2

which factorises to (cosa)^2 + (sina)^2)^2 which is obviously 1^2 = 1.

Did anyone else do it this way and if not will I still get the marks?...

You can do it any method you choose providing you find the correct cartesian equation. If you got what was on the paper, you'll get the marks.
2. used trail and error for the speed question in comprehension, got the speed value of 100 so will i get full marks doing it this way?
yeah that's right.

Values for theta for the last part of question people? I only seem to get the one in the correct domain.
I got something like 6.02 and -0.2 or something which was obviously outside of the 0 to 2pi range
4. I doubt it. I would think that differentiating the given equation would be the desired method.
5. what did people put for the last part of the comprehension, A B or C?
6. I put C but there seems to be a fair majority who put B.
I put C but there seems to be a fair majority who put B.
same but how did they justify it?, i would have thought metres would have been the most appropriate since the calc. came to 160.90 or something so it makes sense to round it to the nearest metre?
8. I went for B: when you multiplied the miles by the value of conversion they gave you, the number of decimal places seemed to correspond to intervals of 10cm (or 0.0001 km)
9. I'm hoping the last question had multiple answers and was just how you justified it <_< because I went with C
10. How high do you guys think the grade boundaries will be this year?
11. I'm hoping no higher than 72/90 please.

Don't think it was a difficult paper, but it appears that a lot of people have made mistakes.
12. I messed up totally!!!!!!!
Anyone know what percentage of A2 core 4 is?
13. Has anyone got the paper which they can upload?

Or just section B at least?
14. (Original post by clad in armour)
same but how did they justify it?, i would have thought metres would have been the most appropriate since the calc. came to 160.90 or something so it makes sense to round it to the nearest metre?
when you converted it to km and then made it into metre by multiplying by 100 you got a number say 123456.4 (cant remember the number just the .4)
and so it was rounded to cm as the last sig fig is cm - 40
how would you justify that as being rounded to metres? when if you put it in metres it has cms???
15. Think I did quite well. Hoping for the A*. I don't want to sound too big headed but if anybody has any questions about the exam quote me and ask and I'll try and remember.
16. Think I did quite well. Hoping for the A*. I don't want to sound too big headed but if anybody has any questions about the exam quote me and ask and I'll try and remember.
17. Hi guys, i was reading some of the previous posts and i think there was some confusion with the Rcos(O+a) question, the answers were coming out of range or something.

My angle 'a' was around 1.33 or something.
I think the question was something like:

sqrt(17) x cos(O+1.33) = 2
so:
cos(O +1.33) = 2/sqrt(17)

O + 1.33 = 1.06435 (something like that)

so O = 1.06435 - 1.33 = -0.2656 (which was out of range, so you add 2pi to this)

therefore O = -0.2656 + 2pi = 6.0175 - this answer was in range and worked, i think that is what you had to do. And then you have to find the other possible solution to O.

zoid
18. I'm pretty sure 10 cm is the correct answer. Because the maximum possible error in the conversion factor is 5x10^-7. When this is multiplied by 100 the absolute error will be 5 cm. Therefore it will always be correct to the nearest 10 cm.
19. Think I did quite well. Hoping for the A*. I don't want to sound too big headed but if anybody has any questions about the exam quote me and ask and I'll try and remember
20. For the rcos(theta+ alpha)

I reckon the values were: 6.02, 3.89.

(Original post by Tallon)
....
Since you're offering, what did you put for the last question?

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