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Edexcel Core 3 - 21st June 2016 AM Watch

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    for modulus questions how would you know if theres two solutions without drawing the graph
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    (Original post by penguin234)
    Hi, would anyone be able to explain June 2015 q3 part c to me pls?? I can do parts a and b. I think there was a question like this in the June 2013 R paper as well which was also q3 part c. The 2015 question is this:

    g(ș) = 4cos2ș + 2sin2ș
    Given that g(ș) = R cos(2ș+alpha), where R> 0 and 0 < alpha < 90°,
    (a) find the exact value of R and the value of alpha to 2 decimal places.(3)
    (b) Hence solve, for –90° < ș< 90°,4cos2ș + 2sin2ș = 1, giving your answers to one decimal place.

    Given that k is a constant and the equation g(ș) = k has no solutions,
    (c) state the range of possible values of k.
    So k/r cannot be greater than 1 or less than -1 because cos and sin range is between -1 and 1.

    So k cannot be greater than r or less then -r, therefore r > k > -r

    Edit: misread the question, what i wrote was for k to have solutions.

    For k to have no solutions k/r has to be greater than 1 or less than -1, so k> 1 or k< -1
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    (Original post by metrize)
    So k/r cannot be greater than 1 or less than -1 because cos and sin range is between -1 and 1.

    So k cannot be greater than r or less then -r, therefore r > k > -r

    Edit: misread the question, what i wrote was for k to have solutions.

    For k to have no solutions k/r has to be greater than 1 or less than -1, so k> 1 or k< -1
    Oh yeah, that makes so much sense!! Thank you so much!!!
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    (Original post by Pablo Picasso)
    Sketch

    y = x^2 + 5|x| - 3
    y = x^2 + |5x - 3|

    showing all intersections
    How do you do this one? y = x^2 + |5x - 3|
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    (Original post by 13 1 20 8 42)
    ln((1/2)e^2) = ln(1/2) + ln(e^2) = ln(2^(-1)) + 2 = -ln2 + 2 = 2 - ln2
    Thanks, had a bit of a dense moment

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    (Original post by Don Joiner)
    On iterations questions when you select intervals to show that there is a sign change.. Is it okay to leave your answer in standard form? As the answer you get is almost always very small


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    Yes, the important part is the sign

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    (Original post by Glavien)
    How do you do this one? y = x^2 + |5x - 3|
    sketch the curve for x >= 3/5 which would be y = x^2 + 5x - 3, and then sketch the curve for x < 3/5 which would be x^2 -5x + 3. The curve is continuous and should have a cusp at x = 3/5.
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    (Original post by AMarques)
    sketch the curve for x >= 3/5 which would be y = x^2 + 5x - 3, and then sketch the curve for x < 3/5 which would be x^2 -5x + 3. The curve is continuous and should have a cusp at x = 3/5.
    Yes
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    (Original post by chickenhips223)
    Order food from UBER using code: uberfood16 to get £10 off your first delivery.They don't charge for the actual delivery btw!! and there is no minimum charge.
    lol
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    (Original post by imran_)
    for modulus questions how would you know if theres two solutions without drawing the graph
    You're better off not risking it and drawing a graph to make it far more easier for you.
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    (Original post by pineneedles)
    I'm doing question 5 on this and I'm not getting the right answer

    http://www.madasmaths.com/archive/iy...apers/c3_x.pdf

    Attachment 553022
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    was the answer to the question (2-ln2, 4). I dont wanna check lol in case i ruin the solution
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    (Original post by bat_man)
    was the answer to the question (2-ln2, 4). I dont wanna check lol in case i ruin the solution
    Yeah, that's the right answer

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    Is an inflection point the same as a turning point???
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    (Original post by Engineerrookie)
    Is an inflection point the same as a turning point???
    Inflection points are special turning points. They are neither maxima nor minima.
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    (Original post by 13 1 20 8 42)
    Inflection points are special turning points. They are neither maxima nor minima.
    Like (0,0) on y=x^3?
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    (Original post by Craig1998)
    Like (0,0) on y=x^3?
    Exactly
    edit: Hmm it seems from formal definition that they aren't necessarily stationary points, merely where curvature changes (this means that the second derivative must be zero - so it just requires that the first derivative is constant) However I think at a level you will only care about inflection points which are also stationary, if any at all
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    I keep getting about 86-89 UMS in papers and keep losing marks from the domain range questions and also silly mistakes, can I get 90UMS on Tuesday??


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    (Original post by Don Joiner)
    I keep getting about 86-89 UMS in papers and keep losing marks from the domain range questions and also silly mistakes, can I get 90UMS on Tuesday??


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    I guess it depends if a range/domain question comes up then...
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    hey does anyone have the C34 jan 2016 international paper? sorry if it was already posted!
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    Do you think if I get 69 out of 75 on both C3 and C4 I could get an A*???
 
 
 
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