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    How many significant figures should you use? I've seen people say always use 3 s.f. unless the question says otherwise but in this paper

    http://mei.org.uk/files/papers/c409ju_as36.pdf

    the very last question on paper A 8 iii) says you have to give your answer to 4 s.f. so does anyone know

    And if someone could explain this: Q5 ii) http://mei.org.uk/files/papers/c410ju_weio.pdf

    How does the mark scheme go from Integral 3dy/(y-2)(y+1) =....

    To Integral (1/(y-2) - 1/y+1)dy=.....

    How did they get rid of the 3 and turn the product into a subtraction I dont understand?
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    (Original post by statskid77)
    How many significant figures should you use? I've seen people say always use 3 s.f. unless the question says otherwise but in this paper

    http://mei.org.uk/files/papers/c409ju_as36.pdf

    the very last question on paper A 8 iii) says you have to give your answer to 4 s.f. so does anyone know
    Their marking guidance says

    Wrong or missing units in an answer should not lead to the loss of a mark unless the scheme specifically indicates otherwise. Candidatesare expected to give numerical answers to an appropriate degree of accuracy, with 3 significant figures often being the norm. Smallvariations in the degree of accuracy to which an answer is given (e.g. 2 or 4 significant figures where 3 is expected) should not normally bepenalised, while answers which are grossly over- or under-specified should normally result in the loss of a mark. The situation regardingany particular cases where the accuracy of the answer may be a marking issue should be detailed in the mark scheme rationale. If indoubt, contact your Team Leader.
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    (Original post by statskid77)
    How many significant figures should you use? I've seen people say always use 3 s.f. unless the question says otherwise but in this paper

    http://mei.org.uk/files/papers/c409ju_as36.pdf

    the very last question on paper A 8 iii) says you have to give your answer to 4 s.f. so does anyone know

    And if someone could explain this: Q5 ii) http://mei.org.uk/files/papers/c410ju_weio.pdf

    How does the mark scheme go from Integral 3dy/(y-2)(y+1) =....

    To Integral (1/(y-2) - 1/y+1)dy=.....

    How did they get rid of the 3 and turn the product into a subtraction I dont understand?
    Generally when they state 'giving your answers in decimal' or 'approximate' i always use 4.

    To address the second question, they have used partial fractions from the first section, and then used that result to integrate the previous statement. Check Q5 i).
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    (Original post by statskid77)
    And if someone could explain this: Q5 ii) http://mei.org.uk/files/papers/c410ju_weio.pdf

    How does the mark scheme go from Integral 3dy/(y-2)(y+1) =....

    To Integral (1/(y-2) - 1/y+1)dy=.....

    How did they get rid of the 3 and turn the product into a subtraction I dont understand?
    I'm not an OCR MEI mathematician, but, as above, in part 5(i), you proved that

    \displaystyle \frac{3}{(y-2)(y+1)} \equiv \frac{1}{y-2} - \frac{1}{y+1} so in your DE:

    \displaystyle \int \frac{\mathrm{d}y}{(y-2)(y+1)} = \int x^2 \, \mathrm{d}x \iff \int \frac{3 \, \mathrm{d}y}{(y-2)(y+1)} = \int 3x^2 \, \mathrm{d}x

    Then apply the partial factorisations you found in part 5(i).
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    Does anyone know on this C3 paper why on question 8iii (last question) the mark scheme says sin(x+pi) =-sinx ?

    I was thinking of using a C4 method to expand the brackets but surely that wouldn't be right as this is a C3 exam? help much appreciated btw

    http://www.mei.org.uk/files/papers/c306ju_kw7e.pdf
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    (Original post by blipson)
    Does anyone know on this C3 paper why on question 8iii (last question) the mark scheme says sin(x+pi) =-sinx ?

    I was thinking of using a C4 method to expand the brackets but surely that wouldn't be right as this is a C3 exam? help much appreciated btw

    http://www.mei.org.uk/files/papers/c306ju_kw7e.pdf
    You could expand it out using the addition formula, but for a C3 method, consider the graph of y = sin x. Notice that it has rotational symmetry so e.g. the values of y from x=pi to x=2pi are the same as the values from x=0 to x=pi, just made negative and in the reverse order.
 
 
 
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