MAT Prep Thread - 2nd November 2016

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    (Original post by jamestg)
    Attachment 586746

    Attachment 586746586748

    How do they get (A+B) +B=1
    Let the area of 0-1 be A.
    Let the area of 1-2 be B.

    The first equation says 3 times the area A plus 2 the area B = 7
    The second equation says the area of 0-2 (which is the area of 0-1+1-2) which is A+B, plus the area B = 1.

    So you get 3A+2B=7
    2A+B=1
    and solve for A and B then add them together.
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    (Original post by BurdMan)
    Can someone explain MAT15 Q3 Part VI?

    I have absolutely no idea where they got anything in their solution from.
    bump
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    (Original post by KloppOClock)
    Think of the two equations as equations of lines (sin and cos are just numbers/cooefficients and re-arrange to make \displaystyle y the subject;
    \displaystyle

(sin \theta )y=(cos \theta )x-2 \gets Equation One

(cos \theta )y=1-(sin \theta )x \gets Equation Two



Eqn1:   y= ((cos \theta )x -2) /sin\theta

Eqn2: y= (1-(sin \theta )x)/cos\theta

    As these are both straight lines, they will only have solutions if they intersect.

    Gradient of Eqn1 is Cos/Sin =1/Tan
    gradient of Eqn2 is -Sin/Cos = -Tan

    As those gradient are different, they both are not parallel, so they intersect at some point, so they always have a solution
    Thank You!
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    On the syllabus, under differentiation one of the points is "derivative of a sum of functions". What does this mean? When i search it up it comes up with a different form of differentiation so are we supposed to learn this
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    (Original post by blurred)
    On the syllabus, under differentiation one of the points is "derivative of a sum of functions". What does this mean? When i search it up it comes up with a different form of differentiation so are we supposed to learn this
    AFAIK, it just means that the derivative of f(x) + the derivative of g(x) = the derivative of (f(x) + g(x)). So it means that if you want to differentiate 2x + 5x^2, you'd differentiate 2x (2), differentiate 5x^2 (10x), and add them together (2 + 10x)
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    Hi, can anyone shed any light on 2013 1J multi choice, i can't make sense of some of their justifications in the mark scheme thank you
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    (Original post by Non-Euclidean)
    Hi, can anyone shed any light on 2013 1J multi choice, i can't make sense of some of their justifications in the mark scheme thank you
    All I did was draw a graph, which you can then see the area easily for n=1 and n=2.

    Sub n=1 and n=2 into the four choices and you are left with one choice.
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    Can someone tell me if my answer to question 4 part iii 2013 would still get full marks?
    The questions asks to show \displaystyle Sin\theta+Cos\theta \leq 0.5

    The mark scheme did it by factorising but I did it a lot different. The question says the only thing you are allowed to assume \displaystyle Sin^2\theta+Cos^2\theta=1. Have I made another assumption by showing you can construct a square or is that okay?

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    Can anyone help me with marking? Do you get full marks if you get the right answer or do you have to show ALL the working? Especially in the multiple choice ones.
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    (Original post by Hiling99)
    Can anyone help me with marking? Do you get full marks if you get the right answer or do you have to show ALL the working? Especially in the multiple choice ones.
    multiple choice is you only get the 4 marks if you have ticked the correct box, anything else is zero (you can guess and get full marks). Im unsure about questions 2-7
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    (Original post by KloppOClock)
    multiple choice is you only get the 4 marks if you have ticked the correct box, anything else is zero (you can guess and get full marks). Im unsure about questions 2-7
    Thx, I usually show all working for all the others, it's only question one where my working makes no sense.
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    (Original post by KloppOClock)
    All I did was draw a graph, which you can then see the area easily for n=1 and n=2.

    Sub n=1 and n=2 into the four choices and you are left with one choice.
    hmm..that helped eliminate a and c as the are of n=1 is easily calculated as 1 but for n=2 i not sure the area is so simple since for what n does the graph instantaneously become 3 as opposed to 2, it clearly becomes 4 for x=2 but the area is harder to calculate as the step to 3 isnt obvious (would be log2(3) which i cant work out in my head :P? Did your graph look like a set of stairs kind of thing?
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    (Original post by Hiling99)
    Thx, I usually show all working for all the others, it's only question one where my working makes no sense.
    As long as you make a logical, correct argument without making assumptions, that's all the working you need for 2-5 the mark scheme is only modelled it shouldnt be exactly what you put
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    (Original post by Non-Euclidean)
    hmm..that helped eliminate a and c as the are of n=1 is easily calculated as 1 but for n=2 i not sure the area is so simple since for what n does the graph instantaneously become 3 as opposed to 2, it clearly becomes 4 for x=2 but the area is harder to calculate as the step to 3 isnt obvious (would be log2(3) which i cant work out in my head :P? Did your graph look like a set of stairs kind of thing?
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    if u still dont get it i can explain it over skype
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    (Original post by KloppOClock)
    Can someone tell me if my answer to question 4 part iii 2013 would still get full marks?
    The questions asks to show \displaystyle Sin\theta+Cos\theta \leq 0.5

    The mark scheme did it by factorising but I did it a lot different. The question says the only thing you are allowed to assume \displaystyle Sin^2\theta+Cos^2\theta=1. Have I made another assumption by showing you can construct a square or is that okay?
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    (Original post by KloppOClock)
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    if u still dont get it i can explain it over skype
    Yeah thanks a lot that makes sense, still want to be able to derive it though haha but process of elimination wins this one!
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    (Original post by KloppOClock)
    bump
    hm.. i think you'd probably get all the marks, maybe just for a=b r=0 by saying sinx=cosx for x=45, but that's a pretty cool way of thinking about it
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    (Original post by Non-Euclidean)
    hm.. i think you'd probably get all the marks, maybe just for a=b r=0 by saying sinx=cosx for x=45, but that's a pretty cool way of thinking about it
    thanks, ill add that extra bit to my solution
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    Man, there is not long till the exam at all! My revision has been totally messed up as I needed to have surgery today and these last 3 weeks I have not been able to focus at all. However, I realise not everything goes the way you want it to. I appreciate the posts in this thread and I really need to get my head down.
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    (Original post by alfmeister)
    Man, there is not long till the exam at all! My revision has been totally messed up as I needed to have surgery today and these last 3 weeks I have not been able to focus at all. However, I realise not everything goes the way you want it to. I appreciate the posts in this thread and I really need to get my head down.
    Hope you're okay, still plenty of time to get prepared for it.
 
 
 
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