Thinking about the mean value theorem without geometry

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Discussion Overview

The discussion revolves around understanding the Mean Value Theorem (MVT) without relying on geometric visualization, focusing instead on numerical reasoning and real-world applications. Participants explore how to intuitively grasp the theorem's implications through various examples and analogies.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants inquire about how to conceptualize the MVT using numerical values rather than geometric representations.
  • There is a suggestion that reasoning numerically may lead to approximations, as the mean value might not be rational.
  • One participant proposes that if the function values at two points are equal, it is logical to deduce that there must be a point where the derivative equals zero, using a temperature analogy.
  • Another participant relates the MVT to the concept of average speed, suggesting that at some point during a trip, the instantaneous speed must match the average speed, assuming continuous variation.
  • A different analogy is introduced, comparing the MVT to finding the "center of mass," although the details of this analogy are not fully explored.

Areas of Agreement / Disagreement

Participants express varying degrees of clarity and understanding regarding the MVT without geometric context. There is no consensus on a singular approach or example that effectively conveys the theorem numerically.

Contextual Notes

Some participants note that the original question may be too vague, indicating potential limitations in the clarity of the inquiry. The discussion also touches on assumptions about continuity and the nature of derivatives.

archaic
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Hello guys, is it possible to "see" the mean value theorem when one is only thinking of numerical values without visualizing a graph? Perhaps through a real world problem?
 
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archaic said:
Hello guys, is it possible to "see" the mean value theorem when one is only thinking of numerical values without visualizing a graph? Perhaps through a real world problem?
What do you want to know? A real world problem which can be solved due to the main value theorem? What should numerically mean? Numerically we always only get an approximation, as the likely mean value isn't rational.
 
fresh_42 said:
What do you want to know? A real world problem which can be solved due to the main value theorem? What should numerically mean? Numerically we always only get an approximation, as the likely mean value isn't rational.
By numerically I meant reasoning without resorting to geometry. In other words, how can one foster an intuition for this without seeing a graph?
 
Well, it is a direct consequence of Rolle, so the question reduces to: Can it be "seen" that given ##f(a)=f(b)## we have ##f'(c)=0## somewhere in between. E.g. if the temperature today at 3 p.m. is equal to the temperature yesterday at 1 p.m., do you consider it logical or seen without a graph, that there must have been a minimum or maximum in the meantime?

I'm afraid your question cannot be answered. It is too vague.

Here's another example (question 5):
https://www.physicsforums.com/threads/math-challenge-december-2018.961292/but this is geometry, even if without a graph.
 
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if you think of the derivative as the speed of a moving particle, the mean value theorem concludes that at some point during a trip, the instantaneous speed must equal the average speed for the whole trip. Assuming speed varies continuously, (or just that it satisfies the intermediate value theorem, which is true for derivatives), this is obvious. I.e. the average speed must be somewhere between the maximum and minimum speeds, hence, by virtue of the derivative satisfying the intermediate value theorem, must equal the instantaneous speed at some point.
 
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