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    night all goodluck tomorrow!
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    (Original post by houseo2)
    also lol https://eiewebvip.edexcel.org.uk/Rep...e_20070118.pdf

    question 8 ii
    Literally the most pointless maths question ever.
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    does anyone have a list of formulae that we get in the exam so i know which ones i need to learn overnight?
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    (Original post by houseo2)


    Originally Posted by Arsey
    dx/dy is very easy just differentiate with respect to y

    dx/dy = 2 x 4cos(2y+6) = -8cos(2y+6)

    so flip both sides

    dy/dx = -1/(8cos(2y+6))

    the annoying bit is making it in terms of x


    now if x = 4sin(2y+6)

    x/4 = sin(2y+6)

    so we now need to move sin to the opposite side where it becomes its inverse function - this is called arc sin (sin^-1 on your calc)

    arc sin (x/4) = 2y+6 now sub thi sback into dy/dx to get

    dy/dx = -1/(8cos(arcsin(x/4)))


    thask but it then says 1/2root 16x^2-x^2

    okay

    start from x/4 = sin(2y+6)

    square both sides

    x^2/16 = sin^2(2y+6)

    subtract each side from 1

    1 - x^2/16 = 1 - sin^2 (2y+6)

    use the identity 1 - sin^2 = cos^2

    1 - x^2/16 = cos^2 (2y+6)

    square root both sides

    SQRT (1 - x^2/16) = cos(2y+6)

    now sub this into dy/dx

    dy/dx = -1/(8 SQRT (1 - x^2/16))
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    (Original post by The Magnificent KoloToure)
    Literally the most pointless maths question ever.
    y = arccos x

    cos y = x

    sin (pi/2 - y) = x

    pi/2 - y = arcsin x
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    (Original post by houseo2)
    and 7d for above post
    Hence show that the population cannot exceed 2800.


    as t tends to infinity e^-t tends to zero

    p < 336 / (0.12 + 0) p < 2800
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    (Original post by Arsey)
    y = arccos x

    cos y = x

    sin (pi/2 - y) = x

    pi/2 - y = arcsin x
    thanks whered you get pi over 2 -y from
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    (Original post by houseo2)
    help please 6d where has the -2 gone?

    https://eiewebvip.edexcel.org.uk/Rep...e_20050620.pdf

    and how do you do this
    |x – 1| – 2 = 5x

    |x – 1| = 5x + 2

    so there are two possible solutions

    (x - 1) = 5x + 2 or -(x - 1) = 5x + 2

    -3 = 4x or -1 = 6x

    x = -3/4 or x = -1/6

    however the solution is only x = -1/6 because if you draw y=5x onto the original graph it only cuts on the reflected part of the modulus graph
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    (Original post by houseo2)
    thanks whered you get pi over 2 -y from
    90 degrees

    sin 80 = cos 10
    sin 70 = cos 20
    sin 60 = cos 30

    etc

    sin x = cos (90-x)

    and

    sin (90-x) = cos x
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    last one use cos(a+b) to show cos2x=1-2sin^2x
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    (Original post by *absinthe*)
    does anyone have a list of formulae that we get in the exam so i know which ones i need to learn overnight?
    Its here
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    Thanks for the in depth explanation on ranges and domains of composite functions Arsey.

    The domain of the first function extends to the composite?

    Just did that Jan '010 paper, I had taken the range of g(x) as the domain of f(x).

    Managed to get 73/75 on that. Made a slip on translating a y-intercept. But I had 40 minutes left on the clock, when comes the actual exam I will go over questions like that...
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    There's nothing more I can do really. Wish I could but nothing's going in now
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    (Original post by houseo2)
    last one use cos(a+b) to show cos2x=1-2sin^2x
    use the addition formulae cos(A+B) as given in the formulae book and set both A and B equal to x.
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    (Original post by CMM)
    Thanks for the in depth explanation on ranges and domains of composite functions Arsey.

    The domain of the first function extends to the composite?
    no but it can have an impact on the composite function - working out the overall domain of composite functions can be quite tricky; you need to work backwards though the composite function.
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    good luck everyonee
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    (Original post by Arsey)
    no but it can have an impact on the composite function - working out the overall domain of composite functions can be quite tricky; you need to work backwards though the composite function.
    for the question regarding dy/dx in terms of x would i get full marks if i put it in terms of arcsinx and also how do you use co a+b for the other one thanks.
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    (Original post by Arsey)
    no but it can have an impact on the composite function - working out the overall domain of composite functions can be quite tricky; you need to work backwards though the composite function.
    It is complicated... Why do questions about ranges only give 1-2 marks, and why is it so.. undertaught :|

    Edit: Just cracked it.

    Thanks for the help
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    (Original post by CMM)
    It is complicated... Why do questions about ranges only give 1-2 marks, and why is it so.. undertaught :|

    Edit: Just cracked it.

    Thanks for the help
    I've been wondering that too.
    By "cracked it", do you mean that specific question? Or domains/ranges in general? Because if you have, then I'd really reeeeeallly appreciate any tips. :p:
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    Best of luck everyone!

    This thread will be closed by the time we get back and please make sure you don't make anymore discussion treads until midnight. Also be vigilant on seeing edexcel C3 threads before the deadline and report them please

    Read the announcement at the top of the thread if in doubt with anything.
 
 
 
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