Is the given function differentiable at the endpoints on the interval [0,5]?

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Discussion Overview

The discussion revolves around the differentiability of the function $$f\left(x\right)=\sqrt{x\left(5-x\right)}$$ on the interval [0,5] and its relation to the Mean Value Theorem (MVT). Participants explore whether the function meets the conditions of the MVT, particularly at the endpoints of the interval.

Discussion Character

  • Debate/contested

Main Points Raised

  • Some participants assert that the function is continuous on the interval but not differentiable at the endpoints due to vertical slopes.
  • Others question the understanding of the MVT, suggesting that the theorem allows for the derivative to be undefined at the endpoints as long as the function is continuous and smooth elsewhere.
  • A participant expresses uncertainty regarding where the derivative is undefined, indicating a lack of clarity in the source material.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the differentiability of the function at the endpoints or the implications for the MVT. Multiple competing views remain regarding the interpretation of the theorem and the function's behavior at the endpoints.

Contextual Notes

There are limitations in the discussion regarding the assumptions about the function's continuity and differentiability, as well as the specific conditions under which the MVT applies. The discussion also reflects uncertainty about the definitions and implications of differentiability at endpoints.

karush
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Does the function satisfy the hypothesis of the mean value theorem
On the given interval, give reasons for your answer

$$f\left(x\right)=\sqrt{x\left(5-x\right)},\ \ \left[0,5\right]$$

The graph of this is the top half of a circle

My answer was
It is continuous at all points on the interval but not differential at the endpoints due to vertical slopes.

This answer was not correct.?

MVT $$f'\left(c\right)=\frac{f\left(b\right)-f\left(a\right)}{b-a}$$
 
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karush said:
Does the function satisfy the hypothesis of the mean value theorem
On the given interval, give reasons for your answer

$$f\left(x\right)=\sqrt{x\left(5-x\right)},\ \ \left[0,5\right]$$

The graph of this is the top half of a circle

My answer was
It is continuous at all points on the interval but not differential at the endpoints due to vertical slopes.

This answer was not correct.?

MVT $$f'\left(c\right)=\frac{f\left(b\right)-f\left(a\right)}{b-a}$$

What is your hypothesis about the MVT?
 
Not sure, the book didn't address where $f'$ is undefined
 
karush said:
Not sure, the book didn't address where $f'$ is undefined

I don't think you understand the mean value theorem very well. It states that if your function is continuous everywhere and smooth at all points except the endpoints, then the gradient of any chord on that function is the same as the gradient of the function at some point in between. So your derivative doesn't need to be defined at the endpoints...
 
OK, thanks.
 

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