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Homework Help: Finding the length of the curve (where it gets undefined at t=0)

  1. Jan 25, 2010 #1
    1. The problem statement, all variables and given/known data
    Find the lenght of the curve

    f(x)= x^(1/3)+ x^(2/3), 0≤x≤2

    2. Relevant equations

    L= integral of square root of (1+ (dy/dx)^2 (dx) ) or (1+ (dx/dy)^2 (dy) )

    3. The attempt at a solution

    The problem is that i cannot take the inverse function of that and differentiate it.
    For example, if you are given y=x^(1/3) and asked to find the curve between (-8,-2) and (8, 2),
    1. switch x and y (reverse the x y coordinates so (-2,-8), (2,8) and you have x=y^(1/3)
    2. cube both sides x^3=y
    3, differentiate it : 3x^2=dy/dx
    4, plug that into the formula of L and evaluate it from -2 to 2.

    I cannot do the same for the given function f(x)= x^(1/3)+ x^(2/3), 0≤x≤2
    Because, after switching x and y, x=y^(1/3)+y^(2/3) +y^(2/3), even if you differentiate it, you cannot isolate y and define dy/dx only in terms of x.

    What should i do?
  2. jcsd
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