# Integral dw/rdr

1. Jun 23, 2008

### harpreet singh

Plz explain me how can i integrate dw/rdr

2. Jun 23, 2008

### harpreet singh

plz help me with this..

3. Jun 23, 2008

### Hootenanny

Staff Emeritus
Could you perhaps explain you question further?

4. Jun 23, 2008

### harpreet singh

w is a function of r and i need to integrate dw/rdr with respect to r

5. Jun 23, 2008

### rock.freak667

you mean you want to find

$$\int \frac{1}{r} \frac{dw}{dr} dr$$

?

6. Jun 23, 2008

### harpreet singh

Ya exactly..

7. Jun 23, 2008

### harpreet singh

I was trying it by using by parts.. By taking 1/r as the first function. But with that i m getting the answer zero..

8. Jun 23, 2008

### rock.freak667

Do you happen to know what dw/dr is ?

9. Jun 23, 2008

### harpreet singh

w is a function of r here.. So it can be written as dw(r)/dr

10. Jun 24, 2008

### nicksauce

I'm sorry but this just seems silly. It's like asking, how do I do the integral $$\int{f(x)dx}$$. The answer to this question will clearly depend on what f(x) is. Here, the answer to your question will depend on what kind of function w(r) is. So unless you give us more information, I don't think we can help you.

11. Jun 24, 2008

### harpreet singh

Actually I am calculating the value of w(r) from a differential equation.. And in satisfying the boundary conditions I need to know that integral to calculate the valuues of constants. As of now w(r) is unknown.

12. Jun 24, 2008

### Defennder

Then I suggest you post the question. We won't know how to help if we don't know exactly what the question is asking for.

13. Jun 24, 2008

### HallsofIvy

Staff Emeritus
Going back to the original question, which I suspect is NOT the question you are really asking,

[tex]\int (dw/dr)dr= w(r)+ C[tex]
where C is an arbitrary constant, by the fundamental theorem of calculus.