Double Integrals: Limits Explained

In summary, there may be situations where the limits in a double integral are in opposite directions, depending on the region being integrated over. This can happen when the region is split into two separate parts, with each part having its own set of limits. It is important to carefully consider the region and its boundaries when determining the limits for a double integral.
  • #1
coverband
171
1
On my post titled double integrals you explained why limits go from x^2 to x when integrating wrt y (i.e. the "bottom" graph is the bottom limit) however i seem to have found a webpage that disagrees with you http://www.libraryofmath.com/double-integral-over-a-more-general-region.html example (d) has limits in opposite direction you stated.
 
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  • #2
coverband said:
On my post titled double integrals you explained why limits go from x^2 to x when integrating wrt y (i.e. the "bottom" graph is the bottom limit) however i seem to have found a webpage that disagrees with you http://www.libraryofmath.com/double-integral-over-a-more-general-region.html example (d) has limits in opposite direction you stated.

It doesn't disagree, you just have to consider 2 different regions there since y = x - 1 isn't always below y^2 = 2x + 6. In fact on the interval [-3, -1], y = x - 1 doesn't even come to play. On that interval, the "lower" branch of your "parabola" (y = -sqrt(2x + 6)) is the lower bound and the "upper" branch (y = sqrt(2x + 6)) is the upper bound. However when you go to the interval [-1, 5], y = x - 1 is is the lower limit and the "upper" branch of y^2 = 2x + 6 is the upper bound.
 

1. What is a double integral?

A double integral is a type of mathematical calculation that involves finding the area under a curved surface in a two-dimensional space. It is an extension of the concept of a single integral, which calculates the area under a curve in a one-dimensional space.

2. What are the limits in a double integral?

In a double integral, the limits represent the boundaries of the region over which the calculation is being performed. They determine the range of values for the two variables used in the integral.

3. How do you determine the limits for a double integral?

The limits for a double integral are typically determined by the shape and size of the region over which the calculation is being performed. They can also be determined by the equations that define the boundaries of the region.

4. Why are limits important in double integrals?

Limits are important in double integrals because they define the boundaries of the region over which the calculation is being performed. They determine the range of values for the variables used in the integral, and without them, the calculation would not be possible.

5. What is the significance of the order of integration in double integrals?

The order of integration in a double integral determines the direction in which the integration is performed. This can affect the complexity of the calculation and the final result. It is important to choose the correct order of integration based on the given problem to ensure an accurate solution.

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