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Homework Help: Question re: difference between Δx and dx

  1. Oct 23, 2011 #1
    2. Relevant equations

    dL = L0αdT

    ΔL = L0αΔT

    These two equations are both listed separately on my equation sheet. How are the dL and ΔL terms different?
  2. jcsd
  3. Oct 23, 2011 #2
    I think that Δx could just indicate a change in something. In physics for example,
    Δx = x2 - x1

    dx however, indicates the infinitesimal change in x.
  4. Oct 23, 2011 #3


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    Gold Member

    Take for instance a curved line.
    You want to find the slope m of the curve at point (x,y).

    There are a few procedures such as the tangential rule or the secant rule.

    But simplictically, assume x is midway between 2 points x1 and x2, and y is midway between corrsponding points y1 and y2.
    Then m = (y2-y1)/(x2-x1)
    Or, m= Δy / Δx ( if y2-y1 and x2-x1 are not too great )

    As Δx or Δy is made to become smaller and smaller to the limit of approaching 0(zero)
    Then m=dx/dy
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