- #1
Chris L T521
Gold Member
MHB
- 915
- 0
Here's this week's problem!
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Problem: Show that if $d$ is a metric for $X$, then \[d^{\prime}(x,y) = \dfrac{d(x,y)}{1+d(x,y)}\]
is a bounded metric that gives the topology of $X$.
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Hint: [sp]If $f(x)=x/(1+x)$ for $x>0$, use the mean value theorem to show that $f(a+b)-f(b)\leq f(a)$.[/sp]
Remember to read the http://www.mathhelpboards.com/showthread.php?772-Problem-of-the-Week-%28POTW%29-Procedure-and-Guidelines to find out how to http://www.mathhelpboards.com/forms.php?do=form&fid=2!
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Problem: Show that if $d$ is a metric for $X$, then \[d^{\prime}(x,y) = \dfrac{d(x,y)}{1+d(x,y)}\]
is a bounded metric that gives the topology of $X$.
-----
Hint: [sp]If $f(x)=x/(1+x)$ for $x>0$, use the mean value theorem to show that $f(a+b)-f(b)\leq f(a)$.[/sp]
Remember to read the http://www.mathhelpboards.com/showthread.php?772-Problem-of-the-Week-%28POTW%29-Procedure-and-Guidelines to find out how to http://www.mathhelpboards.com/forms.php?do=form&fid=2!