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Anyone help me pls !

  1. May 12, 2009 #1
    It is just how can you comment on the key features of the graph ?
  2. jcsd
  3. May 12, 2009 #2


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    I assume you are given a map f(x) and need to comment on its graph?

    Surely there is an example in your textbook of such commenting. Usually one points out at which points there are local and global minima and local and global maxima, where there are saddle points, where there are inflexions points. Also relevant may be to indicate the global behavior of the map: is it bounded above? below? Is there asymptotic behavior?
  4. May 12, 2009 #3
    sorry as i give less info of my graph.

    I was given a graph of V'(x) and is asked to comment on the graph.

    The graph has an x - int as 1.55, part of a graph on LHS of this point is above the x-axis and RHS is below until it reaches 2pi (also an x- int)

    Thx for ur help
  5. May 12, 2009 #4
    Btw, i am doing an analysis task and there is a ques abt practical problem in creating an open cylinder with max volume. How do answer this ?

    The Volume increases as the height increase. dV/dh = -(A^2)/ 4pih^2
  6. May 12, 2009 #5


    Staff: Mentor

    No it doesn't. According to the equation you show, the volume decreases as height increases. Assuming that A and h are positive (a reasonable assumption), dV/dh is always negative. You haven't given us the problem explanation, but I'm guessing that the cylinder is made from a fixed amount of material, so increasing the height causes the area of the base to get smaller, causing the volume to get smaller.

    Have you graphed dV/dh versus h? What questions are you supposed to answer?
  7. May 12, 2009 #6
    Idk how to graph the ques
    sorry ty 4 ur help
  8. May 12, 2009 #7


    Staff: Mentor

    Do you know how to graph y = -1/x2? The function in your problem looks a lot like this.

    Also, what are you asked to do in this problem? Please try to answer in complete words, not textspeak.
  9. May 13, 2009 #8
    We have an equation : V=(92pi-x)^2sqrt(4pix -x^2) )/ (24pi^2)
    Sketch the graph of dV/dh and give comment on the key features of this graph

    Sorry for giving unclear info ! Thx 4 ur time LOL
  10. May 13, 2009 #9


    Staff: Mentor

    The equation you just gave has V as a function of x, not h, so it doesn't make any sense to talk about dV/dh unless there is some relationship between x and h.

    Are you supposed to graph dV/dx and talk about its key features?

    What key features are you supposed to comment on?
  11. May 14, 2009 #10
    my bad , sorry i was in hurry ! You were rite ! It is dV/dx
  12. May 14, 2009 #11
    it just say sketch the graph and comment on key feature
  13. May 14, 2009 #12


    Staff: Mentor

    So the problem statement is this:
    For this function,
    [tex]V = \frac{(92\pi - x)^2 \sqrt{4\pi - x^2}}{24\pi^2}[/tex]
    1. Calculate dV/dx.
    2. Comment on key features of the graph of dV/dx.
    Do you know any rules of differentiation? The ones that would be very useful here are the constant multiple rule, product rule, chain rule, in that order. That's a hint.

    Have you asked your teacher for clarification on what is meant by "key features?"
  14. May 14, 2009 #13
    LOL, he wont tell as this is an analysis task ! I did ask him but he didnt answer. He kinda mean !

    Ty , Mark !
  15. May 14, 2009 #14


    Staff: Mentor

    It would be helpful if you answered each question I ask.
    If you did, we might be a little further along in this problem. With 14 posts in this thread, I can't see that you have actually done anything.

    Speaking of the problem, it seems to have shifted around somewhat in this thread. You first described it this way in post 4:
    Then it turned into this in post 8:
    Are you asking about two different problems?
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