Solve Integration: 4π∫x√(x2+2x+1)/4x

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In summary, the loop 9y^2=x(3-x)^2 is revolved about the y-axis. Find the area of the surface generated this way.
  • #1
elitespart
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The loop 9y^2=x(3-x)^2 is revolved about the y-axis. Find the area of the surface generated this way.

I just need help with integration:

[tex]4\pi\int x\sqrt{\frac{x^{2}+2x+1}{4x}}[/tex]

I know I can pull out the 4 but after that I'm lost. Any suggestions?
 
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  • #2
x^2+2*x+1=(x+1)^2. There's another thing you can pull out.
 
  • #3
oh sweet. Thanks. oh if anyone has time to check could you please let me know if I set up the integral properly?
 
  • #4
You know there is something special about problems like surface area and arc length? With that square root in them, you can almost never do them exactly. You have to set up a problem carefully to get it to have an exact solution. Since yours cracked so easily, I'm going to guess it's correct, just based on probability. But, sure, I'll check it.
 
  • #5
Dick said:
You know there is something special about problems like surface area and arc length? With that square root in them, you can almost never do them exactly. You have to set up a problem carefully to get it to have an exact solution. Since yours cracked so easily, I'm going to guess it's correct, just based on probability. But, sure, I'll check it.

thanks. and I forgot to add that it's from 0 to 3. and you're right - I ended up with 60.9422...
 
Last edited:
  • #6
It looks pretty good as far as the integral goes. Why do you have 4pi instead of 2pi. I might just be getting tired.
 
  • #7
Dick said:
It looks pretty good as far as the integral goes. Why do you have 4pi instead of 2pi. I might just be getting tired.

Because I'm only considering the top half of the loop in the integral.
 
  • #8
Oh. So there's negative y's as well. I was getting tired. Carry on.
 
  • #9
lol no worries. Thank you again.
 

1. What is integration?

Integration is a mathematical process that involves finding the area under a curve in a given interval. It is essentially the reverse of differentiation, and it is used to find the original function when its derivative is known.

2. What is the fundamental theorem of calculus?

The fundamental theorem of calculus states that integration and differentiation are inverse operations. This means that if we integrate a function and then differentiate the result, we will get back the original function.

3. How do you solve a definite integral?

To solve a definite integral, we first need to find the indefinite integral of the function. Then, we can evaluate the indefinite integral at the upper and lower limits of the given interval and subtract the results to find the definite integral.

4. What methods can be used to solve integrals?

There are several methods that can be used to solve integrals, including substitution, integration by parts, trigonometric substitution, partial fractions, and tabular integration. The method used depends on the complexity of the integrand.

5. Can you explain the steps to solve the given integral: 4π∫x√(x2+2x+1)/4x ?

First, we can factor out the 4 from the integral and simplify the expression under the square root. Then, we can use the substitution u = x^2 + 2x + 1 to simplify the integrand even further. Next, we can use the power rule to integrate the resulting expression. Finally, we can evaluate the integral at the upper and lower limits of the given interval and subtract the results to find the definite integral.

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