Double Integrals: Limits Explained

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    Integrals Limits
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SUMMARY

The discussion clarifies the limits of double integrals, specifically addressing the integration with respect to y where limits transition from x^2 to x. It highlights a disagreement found in an external source regarding the limits of integration in example (d) of a double integral over a general region. The key takeaway is that the limits depend on the specific intervals being considered, such as [-3, -1] and [-1, 5], where different functions serve as the lower and upper bounds. Understanding these distinctions is crucial for accurate double integral calculations.

PREREQUISITES
  • Understanding of double integrals in multivariable calculus
  • Familiarity with the concepts of upper and lower bounds in integration
  • Knowledge of piecewise functions and their graphical representations
  • Ability to analyze regions defined by curves and lines
NEXT STEPS
  • Study the properties of double integrals in multivariable calculus
  • Learn how to determine limits of integration for different regions
  • Explore the graphical interpretation of piecewise functions
  • Investigate examples of double integrals over non-standard regions
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Students and educators in mathematics, particularly those focusing on calculus, as well as professionals working with mathematical modeling and integration techniques.

coverband
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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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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.
 

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