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Sketching the change in a cube's volume

  1. Jun 20, 2005 #1
    Hi all,
    I've come by an interesting while studying. Here it goes

    The volume [itex]V=x^3[/itex] of a cube of with edges of length x increases by an amount [itex]\Delta V[/itex] when x increases by an amount [itex]\Delta x [/itex]. Show with a sketch how to represent [itex]\Delta V[/itex] geometrically as the some of the volumes of

    (a) Three slabs of dimensions x by x by [itex]\Delta x [/itex]
    (b) Three bars of dimensions x by [itex]\Delta x [/itex] by [itex]\Delta x [/itex]
    (c) One cube of dimensions [itex]\Delta x [/itex] by [itex]\Delta x [/itex] by [itex]\Delta x [/itex]

    The differential formula [itex]dV=3x^2*dx[/itex] estimates the change in V with three slabs.

    Well that is kinda interesting right? Why is it so? I think the rest (3 bars and a cube) is the error in the estimate. It it right?
  2. jcsd
  3. Jun 20, 2005 #2


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    Science Advisor

    Yes, that's true and I agree that it is interesting!
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