Can the Subdifferential of a Non-Convex Function at a Point be Computed?

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SUMMARY

The discussion centers on computing the subdifferential of the non-convex function defined as f(x) = x² sin(1/x) for x ≠ 0 and f(0) = 0. Participants express confusion regarding the applicability of subdifferentiation to non-convex functions, particularly at the origin. The original poster (OP) seeks a formula or method for determining the subdifferential at this point, noting that while the function is not convex, it is part of an assignment. Graphical analysis indicates that both sides of the function approach zero, suggesting a slope of zero at the origin.

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  • Understanding of subdifferentiation and its definitions.
  • Familiarity with non-convex functions and their properties.
  • Basic knowledge of calculus, particularly limits and derivatives.
  • Experience with graphing functions to analyze behavior around critical points.
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  • Study the concept of subdifferentials in non-convex functions.
  • Learn about the properties of convex and non-convex functions.
  • Explore graphical methods for analyzing function behavior near critical points.
  • Review examples of subdifferentiation from advanced calculus or optimization textbooks.
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Students in advanced calculus or optimization courses, mathematicians interested in non-convex analysis, and anyone seeking to understand subdifferentiation in the context of non-convex functions.

braindead101
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Define f:R->R by
f(x) = { x^2 sin(1/x) x!=0, 0 x=0
Compute subdifferential f(0)

I went through my notes on subdifferentiation and still do not have a clue how to do this process, is there a formula to directly do this? any help would be greatly appreciated.
 
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On the entire of the world wide web, the first result on "subdifferentiation" comes from this thread. What exactly is subdifferentiation?
 
Ok with that definition:

What makes you (the OP) think that we can find the subderiavative at zero? Is the function convex...
 
the function is not convex. but it is an assignment question so it must be doable some how.
so i looked at the wiki you sent me and saw the example. but then i guess it is not the same
as my question as that function is convex and mine is not.
Example i am referring to:
Consider the function f(x)=|x| which is convex. Then, the subdifferential at the origin is the interval [−1, 1].

But with that said, I graphed the x^2sin(1/x) function to try to see the behaviour around 0, and both sides are approaching 0 and the slope seems to be also 0.. but i don't know if this is how to actually do it.

what are your thoughts after that wiki read?
 

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