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    Can anyone answer this quest

    x= cost y= sin2t 0<t<2pie
    a) How express dy/dx in terms of t
    b) Values of parameter t at points where dy/dx=0
    c) Exact points of curve where tangents are parallel to x axis
    d) Show cartesian equation for part of curve 0<t<pie is y= 2xsqrt(1-x)^2

    Thanks
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    x = cos(t)
    y = sin(2t)

    dy/dt = 2cos2t

    dx/dt = -sint
    dt/dx = -1/sint

    a)

    dy/dx = dy/dt * dt/dx = 2cos2t * -1/sint = -2cos2t/sint

    b)

    -2cos2t/sint = 0
    cos2t = 0
    t = pi/4, 3pi/4, 5pi/4, 7pi/4

    c)

    plug values above in.

    d)
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    (Original post by chewwy)
    x = cos(t)
    y = sin(2t)

    dy/dt = 2cos2t

    dx/dt = -sint
    dt/dx = -1/sint

    a)

    dy/dx = dy/dt * dt/dx = 2cos2t * -1/sint = -2cos2t/sint

    b)

    -2cos2t/sint = 0
    cos2t = 0
    t = pi/4, 3pi/4, 5pi/4, 7pi/4

    c)

    plug values above in.

    d)
    thanks could you do part c more slowly?
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    (Original post by evapatel)
    thanks could you do part c more slowly?
    you just put the values you got for t in part b) into the equations you were given at the start (x=cos(t), y=sin(2t)), and you have the points where the line is parallel to the axis (because dy/dx = 0). hope that helps!
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    (Original post by pratikv)
    you just put the values you got for t in part b) into the equations you were given at the start (x=cos(t), y=sin(2t)), and you have the points where the line is parallel to the axis (because dy/dx = 0). hope that helps!
    Thankss
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    (Original post by evapatel)
    Thankss
    no worries. by the way, did you manage to get your halls sorted?
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    (Original post by pratikv)
    no worries. by the way, did you manage to get your halls sorted?
    We haven't been given the accomodation forms yet i was jus wonderin b4 wich ones wer good an i thought we could choose but i realised after you told me that you don't get to choose where you go an u have preferences like location. o wel i'l jus end up wer luck takes me. Thanks 4 ur help neway
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    (Original post by evapatel)
    We haven't been given the accomodation forms yet i was jus wonderin b4 wich ones wer good an i thought we could choose but i realised after you told me that you don't get to choose where you go an u have preferences like location. o wel i'l jus end up wer luck takes me. Thanks 4 ur help neway
    no worries. hopefully i'll see you round next year.
 
 
 
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Updated: December 8, 2005

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