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Mr M's OCR (not OCR MEI) Core 2 Answers May 2012 <strong><font

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    (Original post by kenann)
    Q4) solve 4cos^2+7sinx-7=0, between 0 and 360

    4(1 - (sinx)^2 ) + 7sinx - 7

    = - 4sinx^2 + 7sinx - 3 = 0

    4sinx^2 - 7sinx + 3 = 0

    (4sinx - 3) (sinx - 1) = 0

    therefore sinx = 3/4 and 1

    sin^-1(3/4) = 48.6 and (180 - 48.6)

    sin^-1(1) = 90

    therefore, x = 48.6, 90 and 131.4
    Thanks I realised that i misread -7 for -8 so factorised it wrong! Stupid mistake!
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    (Original post by hannah1994)
    I stupidly didn't read the pi after the 45 in question 3, but did everything else right. How many marks will i lose? Also if you left the answer as 5/root 29 for 7ai will you lose any marks seeing as it was just a 2 mark question? Also for the 2nd part I got the right answer (apart from minus sign), but again didn't simplify my surd. do you reckon I'll have lost any marks?
    Q3 drop 1 mark

    7ai fine

    7aii drop 1 mark
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    (Original post by saj1994)
    HI Mr M,

    On Q2ii) i got the wrong value for c instead of getting -4 i got -22, i did all the working out correct but i think its a calculation error, how many marks would i get for this?

    On Q5aii) I put the sequence repeats itself every 2 terms, would i get a mark for this.

    On Q7 I used the SOH CAH TOA rule and the pythagoras rule to get different answers would get any marks for this.
    Q2 prob drop 2 marks

    Q5 fine

    Q7 no marks - it isn't a right angled triangle
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    Sorry for asking again, but it got buried earlier.
    I didn't notice it asking for exact answers for question 7a so I worked them out to 3s.f.

    Because I didn't realise that they had to be exact, my working was basically just using arctan etc.
    I got all the right answers, but not exactly.

    Is it worth any marks?
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    (Original post by IShouldBeRevising_)
    Mr M last question please, Do you think this papers was hard relative to the other c2 papers, also what raw mark do you think will be an A, Thanks
    about the same as usual in terms of difficulty and i don't guess boundaries
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    (Original post by Mr M)
    Q3 drop 1 mark

    7ai fine

    7aii drop 1 mark
    Ahh good
    Thankyou for doing another markscheme - very helpful!!!
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    (Original post by Mr M)
    about the same as usual in terms of difficulty and i don't guess boundaries
    Ok thanks
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    (Original post by Mr M)
    I don't know what you did so can't say but it doesn't look promising.
    I used rules of logs to do it but obviously must have got something wrong somewhere because I ended up getting -1 with lots of decimal places, would using log rules to get that as my answer get me anything?
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    (Original post by sj_1995)
    If, foolishly, I did (3+2x)^5 - (3-2x)^5 instead of plus, would I get any marks? Im sure i read somewhere in an Old OCR mark scheme there was a mark for correct working put incorrect question copying!

    Or am I dreaming....

    Other than that really happy with the paper!
    That's exactly what I did! Even now I'm determined that the question asked that, I always double check my paper at the end... :/

    Mr M was it definitely (3+2x)^5 + (3-2x)^5? It wasn't the first one take away the next?
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    (Original post by J DOT A)
    Yeah MR M, I used the formula for segment...A=0.5r^2(theta-sintheta) with a value of 15/sqrt pi, would I get 2 method marks out of 3 for using the formula?
    It's just that my r value was incorrect.

    Also, You said I might loose 2 marks for getting incorrect r value..but wouldn't there be on for method?

    Finally, for 7ii I got that answer but postive, I used a triangle and did the acute angle..how many marks would I drop?
    Yes for segment

    Doesn't look like your method for r was right? If it was, 1 mark

    Q7 drop 1 mark
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    (Original post by TehCoolNerd)
    Sorry for asking again, but it got buried earlier.
    I didn't notice it asking for exact answers for question 7a so I worked them out to 3s.f.

    Because I didn't realise that they had to be exact, my working was basically just using arctan etc.
    I got all the right answers, but not exactly.

    Is it worth any marks?
    No I don't think you will get anything there, sorry!
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    (Original post by Nuttyclorox)
    That's exactly what I did! Even now I'm determined that the question asked that, I always double check my paper at the end... :/

    Mr M was it definitely (3+2x)^5 + (3-2x)^5? It wasn't the first one take away the next?
    i'm positive it is definitely +, i looked at it carefully... sorry

    about both your misfortune and the terrible pun
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    (Original post by propertimbo)
    I used rules of logs to do it but obviously must have got something wrong somewhere because I ended up getting -1 with lots of decimal places, would using log rules to get that as my answer get me anything?
    I don't think you will get anything, 1 mark at most by the sound of it
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    Here is the question paper from today, scanned: Name:  C2 Jun12 (1).jpeg
Views: 287
Size:  298.6 KBName:  C2 Jun12 (2).jpeg
Views: 275
Size:  334.0 KB
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    (Original post by kenann)
    i'm positive it is definitely +, i looked at it carefully... sorry

    about both your misfortune and the terrible pun
    I'm not sure I can let you off for the pun. Hmm
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    Mr M,

    for 9bi) I incorrectly wrote 1 < y < 2 as i thought that r has to be between 0 and 1. Solving logs correctly? Would I obtain any marks whatsoever?

    Also for 9bii) I put log to the base 2 of 64, instead of 8. Continuing with the correct method?
    Would I obtain any marks for this also. Or does it stop once you go wrong. I always get confused about this?

    And for the question 7, I'm also assuming that you would obtain no marks at all for using a decimal?
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    (Original post by tahseen1995)
    Here is the question paper from today, scanned: Name:  C2 Jun12 (1).jpeg
Views: 287
Size:  298.6 KBName:  C2 Jun12 (2).jpeg
Views: 275
Size:  334.0 KB
    Holy **** how did you get that lol
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    Mr M, for Question 7(a), for part (i) I just did Inverse Tan of 2/5 and then found the cosine of that, and put it down in decimal (correct but not the exact value). Did the same thing for part (ii) but found the obtuse angle of course. So both my answers were in decimal and not exact form. How many marks will I drop for that??? Thanks
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    (Original post by Kavzaz)
    Mr M,

    for 9bi) I incorrectly wrote 1 < y < 2 as i thought that r has to be between 0 and 1. Solving logs correctly? Would I obtain any marks whatsoever?

    Also for 9bii) I put log to the base 2 of 64, instead of 8. Continuing with the correct method?
    Would I obtain any marks for this also. Or does it stop once you go wrong. I always get confused about this?

    And for the question 7, I'm also assuming that you would obtain no marks at all for using a decimal?
    9bi) 1 mark

    9bii Not sure what you have done really

    7 no marks for using a decimal
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    (Original post by Mr M)
    Q2 prob drop 2 marks

    Q5 fine

    Q7 no marks - it isn't a right angled triangle
    But for Q7i) i got 5/sqrt(29) which if rationalize the fraction i would have got 5sqrt(29)/29 and for 7ii) i got the answer u got but in positive.
 
 
 
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