Find Length of Curve y=(2/3)(x^2+1)^(3/2)

In summary, to find the length of the given curve, we use the formula L = integral (a,b) √(1+(f'(x))^2)dx, where a and b are the limits of integration and f'(x) is the derivative of the given function. In this case, the derivative of y=(2/3)(x^2 +1)^(3/2) is f'(x) = 2x(x^2+1)^1/2. Plugging this into the formula, we get L = integral (3,9) √(1+4x^4 + 4x^2)dx. Simplifying the expression under the square root, we get L =
  • #1
whatlifeforme
219
0

Homework Statement


find the length of the following curve.


Homework Equations


y=(2/3)(x^2 +1)^(3/2) from x=3 to x=9.


The Attempt at a Solution


f'(x) = 2x^3 + 2x
f'(x)^2 = 4x^6 + 8x^4 + 4x^2

L = integral (3,9) sqrt(1+4x^6 + 8x^4 + 4x^2)
 
Physics news on Phys.org
  • #2
hi whatlifeform! :smile:
whatlifeforme said:
y=(2/3)(x^2 +1)^(3/2) from x=3 to x=9.

f'(x) = 2x^3 + 2x

no, you've got muddled :confused:

try the chain rule again :smile:
 
  • #3
dy/dx = (2x) (x^2 + 1) ^ (1/2)
(dy/dx)^2 = 4x^2 (x^2+1)

L = integral (3,9) sqrt(1+4x^4 + 4x^2)
 
  • #4
whatlifeforme said:
dy/dx = (2x) (x^2 + 1) ^ (1/2)
(dy/dx)^2 = 4x^2 (x^2+1)

L = integral (3,9) sqrt(1+4x^4 + 4x^2)

Yes. Can you see a simplification?
 
  • #5
ie, what is √(4x4 + 4x2 + 1) ? :smile:
 
  • #6
tiny-tim said:
ie, what is √(4x4 + 4x2 + 1) ? :smile:

take the integral of this?
 
  • #7
Write the expression under the square-root as the square of something.
 

FAQ: Find Length of Curve y=(2/3)(x^2+1)^(3/2)

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

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

2. How do you find the derivative of a curve?

You can find the derivative of a curve by using the power rule, chain rule, or product rule, depending on the complexity of the function. In this case, the derivative of y=(2/3)(x^2+1)^(3/2) would be (4/9)x(x^2+1)^(1/2).

3. Can this formula be used for any type of curve?

No, this formula can only be used for finding the length of a smooth curve, meaning it has a continuous first derivative.

4. How do you use the formula to find the length of the given curve?

To find the length of the curve y=(2/3)(x^2+1)^(3/2), you need to first calculate the derivative, then plug it into the arc length formula: ∫√(1+(dy/dx)^2) dx. Next, you need to determine the limits of integration, which would be the points where the curve starts and ends. Finally, you can evaluate the integral to find the length of the curve.

5. Can this formula be used for both parametric and polar curves?

Yes, this formula can be used for both parametric and polar curves with some modifications. For parametric curves, the formula would be ∫√(x'(t)^2+y'(t)^2) dt. For polar curves, the formula would be ∫√(r^2+(dr/dθ)^2) dθ.

Similar threads

Replies
10
Views
1K
Replies
3
Views
846
Replies
9
Views
1K
Replies
4
Views
663
Replies
8
Views
1K
Replies
7
Views
2K
Replies
15
Views
1K
Back
Top