Evaluating a definite integral when a condition is given

In summary, the conversation is about evaluating an integral using a given equation. The attempt at a solution involved replacing f(x) using the equation, but this did not help. The responder suggests using the substitution y = 1/x and then substituting for f(1/y) in the integral. The original poster is unsure if this will work and asks for clarification on the limits of the integral. The responder then explains that the substitution can be used effectively depending on the lower limit of the integral.
  • #1
justwild
53
0

Homework Statement


Given that x[itex]^{2}[/itex]f(x)+f([itex]\frac{1}{x}[/itex])=0, then evaluate [itex]\int[/itex][itex]^{1.5}_{0.6}[/itex]f(x)dx

Homework Equations


The Attempt at a Solution



tried to replace f(x) using the provided equation...didn't help
 
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  • #2
Can you elaborate on how you tried replacing f(x)?
 
  • #3
Have you looked at what happens if you substitute y = 1/x in the integral and the use the equation to substitute for f(1/y)?
(Are you sure you've quoted the bounds correctly? It's not from a lower bound of 0.66666... by any chance?)
 
  • #4
haruspex said:
Have you looked at what happens if you substitute y = 1/x in the integral and the use the equation to substitute for f(1/y)?

well If I do that I shall be returning to the same problem statement...
 
  • #5
justwild said:
well If I do that I shall be returning to the same problem statement...

If the lower limit in the integral is 0.6, you cannot answer the question without knowing more about the function f(x). If the lower limit is 0.6666... = 2/3, you can answer the question without knowing more about f(x).

The substitution u = 1/x DOES work if you do it judiciously!
 

1. How do you determine the bounds of integration when evaluating a definite integral with a given condition?

The bounds of integration are determined by the given condition, which typically involves a relationship between the independent variable and the function being integrated. This condition can be used to set up an equation or inequality that will help determine the lower and upper limits of integration.

2. What are some common conditions that are given when evaluating a definite integral?

Some common conditions include a specific value for the dependent or independent variable, a relationship between the limits of integration, or a known relationship between the function and its derivative.

3. Do I need to use a specific method when evaluating a definite integral with a given condition?

The method used to evaluate a definite integral with a given condition will depend on the specific condition and the function being integrated. Some common methods include substitution, integration by parts, and trigonometric substitution.

4. Can a definite integral with a given condition have multiple solutions?

Yes, a definite integral with a given condition can have multiple solutions, especially when the condition provides a range of values for the integral. In these cases, it is important to carefully analyze the given condition to determine the appropriate bounds of integration.

5. How can I check if my solution for a definite integral with a given condition is correct?

To check your solution, you can use the fundamental theorem of calculus, which states that the definite integral of a function is equal to the difference of its antiderivative evaluated at the upper and lower limits of integration. You can also use a graphing calculator or computer program to verify your solution.

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