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Homework Help: Related Rate Question

  1. May 1, 2012 #1
    Related Rate Question plz help!!

    I am stuck on this question and need help asap plzz.

    Mr. John is climbing a tree at a rate of 2m/s. After 1 second of climbing Mr. John is noticed by a 2m tall zombie that is 30m away from the tree. The zombie walks towards Mr. John at a rate of 5m/s. What is the rate of change of the distance between Mr. John and the zombie when the angle of elevation from the zombie to Mr. John is Pi/4.

    i kno that
    Dy/Dt = 2m/s.
    Dx/Dt is 5m/s.
    theta is Pi/4.
    i just cant find out how to do this plzz help!!
  2. jcsd
  3. May 2, 2012 #2
    Re: Related Rate Question plz help!!

    Write down functions j(t) and z(t), then find the derivative of [itex]\sqrt{j^2(t) + z^2(t)}[/itex]. Note that j and z are lines in R^2 space. jx is always 0 and zy is probably 2.
  4. May 2, 2012 #3
    Re: Related Rate Question plz help!!

    Could you please draw out the situation and then post it up? It would be of big assistance.
  5. May 2, 2012 #4


    Staff: Mentor

    Re: Related Rate Question plz help!!

    Some of what you know isn't true! The angle is a function of time, and is ##\pi/4## only at one particular time. Also, since the zombie (who writes these problems?) is approaching the tree, dx/dt = -5 m/s.
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