How do I Integrate \sqrt{1+x^4+2x^2}?

In summary, the conversation discusses a problem involving the equation y=(1/3)(x^2+2)^3/2 and the integration equation for calculating the arc length of a curve. The individual attempting the problem is stuck on finding the antiderivative and a user provides a hint to solve it by recognizing that x^4+2x^2+1 can be written as (x^2+1)^2.
  • #1
miglo
98
0

Homework Statement


[tex]y=\frac{1}{3}\left(x^2+2\right)^{3/2}[/tex]


Homework Equations


[tex]\int_{a}^{b}\sqrt{1+\left(\frac{dy}{dx}\right)^{2}}dx[/tex]


The Attempt at a Solution


[tex]\frac{dy}{dx}=x\sqrt{x^2+2}[/tex]
[tex]\int_{0}^{3}\sqrt{1+\left(x\sqrt{x^2+2}\right)^{2}}dx=\int_{0}^{3}\sqrt{1+x^4+2x^2}dx[/tex]
I'm stuck with that integral, not sure what the antiderivative for that function would be
Any hints at the next step would be greatly appreciated.
 
Physics news on Phys.org
  • #2
Here's a hint: x4+2x2+1 = (x2+1)2
 
  • #3
Wow I can't believe i didn't see that.
I tried Wolfram Alpha earlier and they used a substitution but i couldn't follow their steps so i decided to consult the Physics Forums.
Thanks Char. Limit.
 

1. What is arc length and how is it related to integrals?

Arc length is the distance along a curve, also known as the length of the curve. Integrals are used to find the arc length of a curve by summing up infinitesimal lengths along the curve. This is known as the arc length integral.

2. How do you find the arc length of a curve using integrals?

To find the arc length of a curve using integrals, you first need to set up the arc length integral, which is the integral of the square root of 1 plus the derivative of the curve squared. Then, you evaluate the integral using appropriate integration techniques, such as substitution or integration by parts.

3. Can you provide an example of finding arc length using integrals?

Yes, for example, to find the arc length of the curve y = x^2 from x = 0 to x = 2, we first set up the arc length integral as: ∫√(1 + (2x)^2) dx. Then, we use the substitution u = 1 + (2x)^2, du = 4x dx to evaluate the integral: ∫√u du. This gives us the arc length of the curve as √(1 + 4^2) - √1 = 4√2 - 1.

4. What are some common mistakes to avoid when using integrals to find arc length?

Some common mistakes to avoid when using integrals to find arc length include forgetting to take the square root of the derivative in the arc length integral, not setting up the integral correctly, and making errors in the integration process. It is important to double check your work and use appropriate integration techniques to avoid mistakes.

5. Are there any other methods for finding arc length besides using integrals?

Yes, there are other methods for finding arc length, such as using the arc length formula for specific curves, such as circles or parabolas. However, the arc length integral is a more general method that can be applied to any curve, making it a useful tool in calculus and physics.

Similar threads

  • Calculus and Beyond Homework Help
Replies
10
Views
436
  • Calculus and Beyond Homework Help
Replies
3
Views
580
  • Calculus and Beyond Homework Help
Replies
22
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
823
  • Calculus and Beyond Homework Help
Replies
2
Views
540
  • Calculus and Beyond Homework Help
Replies
6
Views
849
  • Calculus and Beyond Homework Help
Replies
12
Views
2K
  • Calculus and Beyond Homework Help
2
Replies
47
Views
2K
  • Calculus and Beyond Homework Help
Replies
4
Views
1K
  • Calculus and Beyond Homework Help
Replies
20
Views
453
Back
Top