Lip Functions: Partial Derivatives on Ball Br(p)

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SUMMARY

The discussion establishes that if the partial derivatives of a function \( f: \mathbb{R}^n \to \mathbb{R}^n \) are bounded on a ball \( B_r(p) \), then \( f \) is Lipschitz continuous on that ball. Utilizing the Mean Value Theorem for partial derivatives, it is shown that there exists a point \( c \) in \( B_r(p) \) such that \( f'(c)(x) = \frac{f(x) - f(c)}{||x-c||} \) for all \( x \) in \( B_r(p) \). By defining \( M \) as the maximum of the bounded partial derivatives, the Lipschitz condition \( |f(x) - f(c)| \leq M||x-c|| \) is satisfied, confirming that \( f \) has a Lipschitz constant \( M \).

PREREQUISITES
  • Understanding of Lipschitz continuity
  • Familiarity with partial derivatives
  • Knowledge of the Mean Value Theorem
  • Basic concepts of metric spaces
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  • Study the implications of Lipschitz continuity in analysis
  • Explore the Mean Value Theorem in higher dimensions
  • Investigate applications of Lipschitz functions in optimization
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Mathematicians, students studying real analysis, and anyone interested in understanding the properties of Lipschitz continuous functions and their applications in various fields.

onie mti
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Can i get an idea of how to show that if the partial derivates of the components of a Rn-Rn function f are boounded on a ball Br(p) then f is Lip on the ballI defined f to be a Rn-Rn function defined on a set D
 
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containing Br(p), we must show that f is Lipschitz on Br(p). We can start by using the Mean Value Theorem for partial derivatives. This states that for each component of the function, there exists a point c in Br(p) such thatf'(c)(x) = (f(x) - f(c))/||x-c|| for all x in Br(p). By assumption, the partial derivatives of f are bounded on Br(p). Let M be the maximum of all the partial derivatives. Then, for all x in Br(p), |f(x)-f(c)| ≤ M||x-c||.This implies that f is Lipschitz on Br(p) with Lipschitz constant M.
 

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