Mr M's OCR (not OCR MEI) Core 2 Answers May 2013

I put b as -2 at it was y=4b^x and it crossed the y-axis at (0,4) which is only possible is b is negative.

For 7ii) :
I wrote, Area = 37/30 = 1.23 (3sf)
then underlined the decimal, does this lose a mark?
Thanks in advance

For 7ii) :
I wrote, Area = 37/30 = 1.23 (3sf)
then underlined the decimal, does this lose a mark?
Thanks in advance

$2 - \frac{2}{3} \neq \frac{5}{3}$

7ii) Find the equation of the tangent, then where the tangent meets the x axis. Now calculate the area of the triangle and subtract this from the value of the integral provided previously.

For the perimeter question 5(ii) I calculated the length BD using the formula 2rsin(θ/2) which gave me 12.461....
I then added this to 12.8 and 9 to give an answer of 34.3cm (3sf).
How many marks would I lose for this and why isn't this correct?

I have no idea where that formula appeared from! Drop 2 marks.

If cosx= -1 then x= 2pie/3
Cosine is negative in the 4th quadrant in the |CAST diagram. Therefore surely you would do pie + 2pie/3 in order to get the value of 5pie/3?

Also for question 7(ii).
I correctly found the equation of the tangent and then integrated the line between 4 and 0. I then subtracted this value from the value found in 7(i).
How many marks would I get?

I'm not sure whether you're interseted but I suspect the formula works out the length of BC. You know for triangle BAC, and another triangle BDC with D on the circumference of the circle, angle BDC will be half angle BAC, or half theta. From the extended sine rule, the circumcircle of BCD will be the circle with centre A and radius 16 so:

BC/ sin(half theta) = 2R, so BC = 2Rsin(half theta).

However, germankid has made the mistake that D is not on the circumference of the circle.

Hi Mr M,

Q1 - I worked out the wrong value value of h (stupid I know) but apart from that my method going forward was fine
Q7ii - I differentiated the equation but made a silly mistake and worked out m as 6 instead of 3. From then on however, my method was fine.
How many marks would I lose?
Thanks in advance,
Akash

Mr. M,

Unfortunately on question 3i) I expanded the first binomial incorrectly by using 5C1 and 5C2, as opposed to 6C1 and 6C2. Thus my answer was 64+800x+4000x^2, which I then used in ii) and so got c=-7.25.

How many marks do you think I would lose for this?

Thanks a lot

Mr M's OCR (not OCR MEI) Core 2 Answers May 2013


1. 6.39 (4 marks)


2. (i) 254 and 106 degrees (3 marks)

(ii) 71.6 and 252 degrees (3 marks)


3. (i) $64+960x+6000x^2$ (4 marks)

(ii) c = - 11 (3 marks)


4. (a) $\frac{5}{4}x^4 -3x^2+x+k$ (3 marks)

(b) (i) $-12 x^{-2} + k$ (2 marks)

(ii) a = 2 (3 marks)


5. (i) 62.2 (4 marks)

(ii) 34.0 (4 marks)


6. (i) 963 (3 marks)

(ii) 17 (6 marks)


7. (i) Show ... (4 marks)

(ii) $\frac{37}{30}$ (5 marks)


8. (i) (a) (0, 1) (1 mark)

b) (0, 4) (1 mark)

c) Any value where a > 1 and any value where 0 < b < 1 (2 marks)

(ii) Show ... (5 marks)


9. (i) 15 (2 marks)

(ii) Show f(-0.5)=0 and $f(x)=(2x+1)(2x-3)(x+1)$ (6 marks)

(iii) $\theta = \frac{2\pi}{3}$ and $\theta =\frac{4\pi}{3}$ and $\theta=\pi$ (4 marks)


I'll be around a bit this afternoon and then part of this evening to answer questions. Please post in this thread rather than sending me private messages.

Mr M how many marks would i get for 7ii if i worked out wrong tangent by using wrong x-value, but differentiated correctly, but showed you had to integrate by doing curve- tangent. Therefore, overall wrong area under curve

RE; 8i), I put y=1 and y=4 as my answers instead of (0,1) and (0,4). Will I still get the marks?

drop 2

Hi Mr M,
Do you have a rough idea how many UMS I would get for 68/72?

Mr M's OCR (not OCR MEI) Core 2 Answers May 2013


1. 6.39 (4 marks)


2. (i) 254 and 106 degrees (3 marks)

(ii) 71.6 and 252 degrees (3 marks)


3. (i) $64+960x+6000x^2$ (4 marks)

(ii) c = - 11 (3 marks)


4. (a) $\frac{5}{4}x^4 -3x^2+x+k$ (3 marks)

(b) (i) $-12 x^{-2} + k$ (2 marks)

(ii) a = 2 (3 marks)


5. (i) 62.2 (4 marks)

(ii) 34.0 (4 marks)


6. (i) 963 (3 marks)

(ii) 17 (6 marks)


7. (i) Show ... (4 marks)

(ii) $\frac{37}{30}$ (5 marks)


8. (i) (a) (0, 1) (1 mark)

b) (0, 4) (1 mark)

c) Any value where a > 1 and any value where 0 < b < 1 (2 marks)

(ii) Show ... (5 marks)


9. (i) 15 (2 marks)

(ii) Show f(-0.5)=0 and $f(x)=(2x+1)(2x-3)(x+1)$ (6 marks)

(iii) $\theta = \frac{2\pi}{3}$ and $\theta =\frac{4\pi}{3}$ and $\theta=\pi$ (4 marks)


I'll be around a bit this afternoon and then part of this evening to answer questions. Please post in this thread rather than sending me private messages.