Solving Arc Length Integral for y=ln(1-x^2) - 0 to 1/2

In summary, the problem is to find the length of the curve of y=ln(1-x^2) for x between 0 and 1/2. The attempted solution involved decomposing the integral and encountering a negative sign, which was confusing. The correct solution involves using the formula for arc length of a single variable function, but the signs were still unclear. After receiving help, the problem was solved.
  • #1
hachi_roku
61
0

Homework Statement



ok, the original prob is : find the length of the curve of y=ln(1-x^2) x between 0, 1/2.



Homework Equations





The Attempt at a Solution


ive made it this far: my integral is -1 + 2/1-x^2.....ok so i decompose the second part but in doing so i get a negative to make it -(x+1)(x-1) but i don't know what happens to that negative because the solution manual says the integral is ...-1+ 1/x+1 -1/x-1 dx i don't get the signs. please help!
 
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  • #2
if we are woking with single variable functions, y=f(x) like here then the arc length from a to be of a curve is:


[tex]L=\int_a^b\sqrt{1+[f'(x)]^2}dx[/tex]
 
  • #3
yes...like i said I've already worked that part...im toward the end of the problem i just don't get the signs
 
  • #4
hachi_roku said:
yes...like i said I've already worked that part...im toward the end of the problem i just don't get the signs

Well, since you have shown almost no work(step by step) it is hard to tell where you have missed, or what you are doing wrong.
 
  • #5
got it...nvm..thanks
 
  • #6
hachi_roku said:
got it...nvm..thanks

:cool:
 

1. What is the equation for finding the arc length of a curve?

The equation for finding the arc length of a curve is given by L = ∫√(1 + (dy/dx)^2) dx, where dy/dx represents the derivative of the curve.

2. How do I solve an arc length integral?

To solve an arc length integral, you first need to find the derivative of the given curve. Then, you can plug that derivative into the equation L = ∫√(1 + (dy/dx)^2) dx and integrate it with respect to x from the given limits.

3. Can you provide an example of solving an arc length integral?

Sure, let's take the given equation y=ln(1-x^2) with limits from 0 to 1/2. First, we find the derivative of the curve: dy/dx = -2x/(1-x^2). Then, we plug this into the equation for arc length: L = ∫√(1 + (-2x/(1-x^2))^2) dx. After integration, we get the final answer as L = 0.4338 units.

4. Are there any special cases to consider when solving an arc length integral?

Yes, there are a few special cases to consider. If the curve is a straight line, the arc length will be equal to the distance between the two given limits. Also, if the curve is a circle, the arc length can be calculated using the formula L = rθ, where r is the radius of the circle and θ is the angle between the two given limits.

5. How is finding the arc length of a curve useful in real life?

Finding the arc length of a curve has various applications in real life, such as in engineering, physics, and geometry. It can be used to calculate the length of a curved road or the surface area of a curved object. It is also used in designing roller coasters and calculating the trajectory of a projectile. Overall, it helps us understand and analyze curved shapes and their properties.

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