From 7c66b227a494748e2a546fb85317accd00aebe53 Mon Sep 17 00:00:00 2001 From: Justin Gassner Date: Thu, 15 Feb 2024 05:11:07 +0100 Subject: Update --- pages/general-topology/metric-spaces/index.md | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) (limited to 'pages/general-topology/metric-spaces/index.md') diff --git a/pages/general-topology/metric-spaces/index.md b/pages/general-topology/metric-spaces/index.md index c0dc45a..52b2b4c 100644 --- a/pages/general-topology/metric-spaces/index.md +++ b/pages/general-topology/metric-spaces/index.md @@ -46,13 +46,13 @@ Clearly, a metric subspace of a metric space is itself a metric space. {% proposition %} Let $(X,d)$ be a (semi-)metric space. - For all $x,y,z \in X$ we have the *inverse triangle inequality* - + $$ \abs{d(x,y) - d(y,z)} \le d(x,z). $$ - For all $v,w,x,y \in X$ we have the *quadrilateral inequality* - + $$ \abs{d(v,w) - d(x,y)} \le d(v,x) + d(w,y) $$ @@ -141,27 +141,31 @@ every sequence in $X$ has at most one limit. Let $(X,d_X)$ and $(Y,d_Y)$ be metric spaces. A mapping $f: X \to Y$ is called - *continuous at a point $x \in X$* if - + $$ - \forall\epsilon>0 \ \ \exists\delta>0 \ \ \forall x' \in X : \big\lparen d_X(x,x') \le \delta \implies d_Y(f(x),f(x')) < \epsilon \big\rparen + \forall\epsilon>0 \ \ \exists\delta>0 \ \ \forall x' \in X : + \big\lparen d_X(x,x') \le \delta \implies d_Y(f(x),f(x')) < \epsilon \big\rparen $$ - *continuous* if it is continuous at every point of $X$, that is - + $$ - \forall x \in X \ \ \forall\epsilon>0 \ \ \exists\delta>0 \ \ \forall x' \in X : \big\lparen d_X(x,x') \le \delta \implies d_Y(f(x),f(x')) < \epsilon \big\rparen + \forall x \in X \ \ \forall\epsilon>0 \ \ \exists\delta>0 \ \ \forall x' \in X : + \big\lparen d_X(x,x') \le \delta \implies d_Y(f(x),f(x')) < \epsilon \big\rparen $$ - *uniformly continuous* if - + $$ - \forall\epsilon>0 \ \ \exists\delta>0 \ \ \forall x,x' \in X : \big\lparen d_X(x,x') \le \delta \implies d_Y(f(x),f(x')) < \epsilon \big\rparen + \forall\epsilon>0 \ \ \exists\delta>0 \ \ \forall x,x' \in X : + \big\lparen d_X(x,x') \le \delta \implies d_Y(f(x),f(x')) < \epsilon \big\rparen $$ - *Lipschitz continuous* if - + $$ - \exists L \ge 0 \ \ \forall x,x' \in X : d_Y(f(x),f(x')) \le L \, d_X(x,x') + \exists L \ge 0 \ \ \forall x,x' \in X : + d_Y(f(x),f(x')) \le L \, d_X(x,x') $$ {% enddefinition %} -- cgit v1.2.3-54-g00ecf