OCR (not OCR MEI) Core 3 answers Jan 2011

OCR (not OCR MEI) CORE 3 answers Jan 2011


1. $x=\frac{a}{3}$ or $x=-3a$ (3 marks)


2. Translation 3 units in negative x direction, reflection in x axis, stretch scale factor 4 in y direction. Stationary points (-5, 24) and (-3, 0) (4 marks)


3. $\frac{dA}{dt}=45000 \, cm^2 hr^{-1}$ (3 marks)


4. (i) $25\sin(\theta + 16.3)$ (3 marks)

ii) $\theta = 12.4^\circ$ or $\theta = 135^\circ$ (4 marks)


5. $V=24 \pi \ln 5$ (9 marks)


6. i) $\frac{dy}{dx}=\frac{-2(3x^3-16x-3)}{(x^3-4x^2+2)^2}$ and show ... (4 marks)

ii) (2.398, -1.552) (5 marks)


7. i) $x=\sqrt{e^8 - 8}$ (3 marks)

ii) f has inverse $f^{-1} (x) = e^x$ (3 marks)

iii) $\frac{6}{e^3}$ (3 marks)

iv) 20.3 (3 marks)


8. a) i) 2 positive U shapes and 2 negative inverted U shapes (3 marks)

ii) $\beta = 3\pi - \alpha$ (2 marks)

b) i) (1 mark)

ii) $\frac{225}{322}$ (6 marks)


9. i) a) Show ... (3 marks)

b) Show and (5 marks)

ii) $y \geq 2 \sqrt k$ (5 marks)

Hey guys, question for Mr. M: for 8. a) i) I drew the graph from -4pi to 4 pi (clearly I can't follow simple instructions), assuming the part in the range they asked for was correct will I be penalised for this? Thanks

Thanks Mr M, looks like I've done pretty well despite getting terrible marks in all the past papers.

One question though, for 8ii I put beta=-alpha. I never thought about putting the 3pi in for some reason. Will I lose both marks for that?

1- didnt get -3a
3- didnt not round up
8b ii) got another number, due to wrong number put in, all working rite.
9- left it at x, didnt find y value

how many marks have i lost? thanks!!

Hey guys, question for Mr. M: for 8. a) i) I drew the graph from -4pi to 4 pi (clearly I can't follow simple instructions), assuming the part in the range they asked for was correct will I be penalised for this? Thanks

1- didnt get -3a
3- didnt not round up
8b ii) got another number, due to wrong number put in, all working rite.
9- left it at x, didnt find y value

how many marks have i lost? thanks!!

about 5?

No not if you did that right.

No not if you did that right.

yes sorry

Thanks thought this would be the case but wasn't sure. Your answers are brilliant as usual, really helpful and i'm relatively confident about this one.

And I managed not to cause an argument on here like I did last summer.

for the cosec alpha cosec beta question, i got beta = -alpha -pie

would i get any marks?