Understanding the Concept of Gradient for a Zero Function

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Discussion Overview

The discussion revolves around the concept of the gradient of a function, particularly in the context of a zero function. Participants explore the implications of the gradient of a function that is not constant, specifically comparing it to the gradient of a true zero function.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant proposes that if F(x,y,z) = 0, then the gradient grad(F) should also equal zero.
  • Another participant clarifies that the derivative of a constant is always zero, but questions the assumption that F(x,y,z) = x + y + z is a constant function.
  • A different participant asserts that grad(x+y+z) = <1,1,1> does not equal <0,0,0>, emphasizing that there is no contradiction in the results.
  • One participant expresses confusion about the definition of a zero function, noting that F(x,y,z) = x+y+z is not a zero function and does not have a critical point at (0,0,0).
  • Another participant requests clarification on the initial question, emphasizing that a zero function is defined as F(x,y,z) = 0 for all x, y, and z, which does not apply to F(x,y,z) = x + y + z.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the definition of a zero function and its implications for the gradient. Multiple competing views remain regarding the nature of the function and its gradient.

Contextual Notes

There are unresolved assumptions regarding the definitions of a zero function and the implications of gradients for non-constant functions. The discussion reflects varying interpretations of these concepts.

HAMJOOP
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Suppose F(x,y,z) = 0
grad (F) = 0 ?

e.g. F = x + y + z

grad (F) = <1,1,1> =/= <0,0,0> ??

I don't know why I get an opposite result
 
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What opposite result are you talking about?

The derivative of a constant is always zero, regardless of the value of the constant.

Hint: F(x,y,z) = x + y + z is not a constant function.
 
grad(x+y+z)=<1,1,1> =/= <0,0,0> =grad(0)
x+y+z=/=0

There is no contradiction, why would you expect one?
 
Because if ##F(x,y,z)=x+y+z## then it's not a zero function? And it doesn't have a critical point at (0,0,0) either. Maybe I'm not clear what exactly what you're asking. ##F(x,y,z)=x+y+z## equals zero at zero but the value of a function at one point doesn't tell you anything about the value of its derivative. Derivatives depend on the value of a function in the neighbourhood of the point.
 
Hamjoop, could you please come back and explain more about what you are asking/thinking? A "zero function", to me, is exactly what it says: F(x,y,z)= 0 for all x, y, and z. And that is certainly not true for F(x,y,z)= x+ y+ z. What is your idea of a "zero function"?
 

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