What are the limits of integration for evaluating a double integral?

In summary, the problem is to evaluate the double integral ∫ ∫ R sin(x/y) dA, where R is the region bounded by the y-axis, y=π and x=y^2. The limits of integration are ∫0π ∫0y2 and the challenge is deciding which variable to treat as constant when integrating.
  • #1
ilovemath88
1
0

Homework Statement



Evaluate the following double integral:
∫ ∫ R sin (x/y) dA

where R is the region bounded by the y axis, y=pi and x=y^2

Homework Equations



as in problem statement

The Attempt at a Solution



Well I started this question by drawing the area to be evaluated. From this I chose my limits of integration, however I feel this may be where I am going wrong. I used ∫ (upper y=pi lower y=0) dy and ∫ (upper x=y^2 lower x=0) dx.
Im not sure if this is right first of all, and secondly, sin (x/y) is really tripping me up. This is because when I treat a variable as constant, where is it going. For example if I firstly evaluate sin (x/y) dy, I'm not sure of the result.
 
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  • #2
Hi ilovemath88! Welcome to PF :smile:

(have an integral: ∫ and a pi: π and try using the X2 and X2 tags just above the Reply box :wink:)

Yes, your limits, ∫0π0y2 are correct.

As you say, you have to treat one variable as a constant when you integrate wrt the other …

so which is easier to integrate first, sin(x/y)dx or sin(x/y)dy ? :wink:
 

Related to What are the limits of integration for evaluating a double integral?

What is a double integral?

A double integral is an integral that involves two variables and is used to find the volume under a three-dimensional surface. It is represented by two nested integral signs.

What is the purpose of evaluating a double integral?

The purpose of evaluating a double integral is to find the exact numerical value of the volume under a three-dimensional surface. This is useful in many scientific and engineering applications, such as calculating the mass of an object or the volume of a fluid.

What are the steps to evaluate a double integral?

The steps to evaluate a double integral are: 1) determine the limits of integration for both variables, 2) set up the integral with the appropriate integrand, 3) solve the inner integral first, treating the outer variable as a constant, 4) plug the result into the outer integral and solve, 5) if necessary, repeat steps 3 and 4 for any remaining nested integrals.

What are some common methods for evaluating a double integral?

Some common methods for evaluating a double integral include using the fundamental theorem of calculus, using iterated integrals, and using change of variables. The method used will depend on the complexity and type of the integral.

How can I check my answer when evaluating a double integral?

One way to check your answer when evaluating a double integral is to use a graphing calculator or computer software to plot the surface and use the numerical integration function to find the volume. You can also check your answer by calculating the integral using a different method, such as using polar coordinates instead of rectangular coordinates.

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