Does integration give area between graph and x axis?

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Discussion Overview

The discussion revolves around the concept of integration and its relationship to calculating the area between a graph and the x-axis. Participants explore the implications of integrating functions that may lie above or below the x-axis, as well as the conditions under which these areas are defined.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions whether integration can find the area between a curve and the x-axis without restrictions, suggesting that it may lead to infinite results.
  • Another participant clarifies that the term "area under a curve" typically assumes the curve is above the x-axis, outlining the boundaries for a definite integral.
  • It is noted that if the curve is below the x-axis, the area is counted with a negative sign, indicating a subtraction from the total area.
  • A different perspective suggests that when the curve is below the x-axis, the area calculated is actually above the curve, between the curve and the x-axis.
  • Further elaboration indicates that if the entire graph is below the x-axis, the total area will be counted as negative, while acknowledging the concern about the sign of the result.

Areas of Agreement / Disagreement

Participants express differing views on how to interpret the area calculated by integration, particularly regarding curves that lie below the x-axis. There is no consensus on whether the area should be considered positive or negative, and the discussion remains unresolved.

Contextual Notes

Participants highlight the importance of defining the boundaries of integration and the implications of the curve's position relative to the x-axis, but do not resolve the mathematical nuances involved.

CAH
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Does integrating find the area between the curve and x-axis (regarless of it being a smile/frown or any other graph)?
I've heard people say its the area UNDER a curve...
but then how would you even get a definit answer surely it may be infinite if there's no restrictions?

Thanks
 
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When people call it the area "under a curve", there is still the implicit assumption that it is above the x axis.

For a definite integral from a to b, you would be calculating the area of a region bounded as follows:

On the left by the vertical line defined by x=a
On the right by the vertical line defined by x=b
On the bottom by the horizontal line defined by y=0
On the top by the graph of the function.
 
Note that if the curve is below the x-axis then this area is counted with a minus sign
 
If it's below the x-axis is it calculating the area above the curve, between the curve and the x-axis above it
 
As jk22 pointed out, the areas of any regions where the graph is below the x-axis count as subtractions from the total area, not as additions. If the entire graph is below the x-axis then the entire area will be counted as negative.

But yes, other than this concern about the sign of the result, it is calculating the area above the graph and below the x axis.
 

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