Math Help Forum

Math Help Forum Feed Site Feed

Go Back   Math Help Forum > University Math Help > Discrete Mathematics, Set Theory and Logic
Reply
 
Thread Tools Display Modes
  #1  
Old July 5th, 2009, 04:23 PM
Junior Member
 
Join Date: Nov 2008
Posts: 47
Country:
Thanks: 14
Thanked 0 Times in 0 Posts
tukilala is on a distinguished road
Default create function

can someone help me please build 2 bijection(injective and surjective) functions:
1. from (0, 1) to (0,infinite )
2. from (0,1) to [0,infinite)

thanks.
Reply With Quote
Advertisement
 
  #2  
Old July 5th, 2009, 05:22 PM
MHF Contributor

 
Join Date: Aug 2006
Posts: 6,715
Thanks: 68
Thanked 2,485 Times in 2,279 Posts
Plato has a reputation beyond reputePlato has a reputation beyond reputePlato has a reputation beyond reputePlato has a reputation beyond reputePlato has a reputation beyond reputePlato has a reputation beyond reputePlato has a reputation beyond reputePlato has a reputation beyond reputePlato has a reputation beyond reputePlato has a reputation beyond reputePlato has a reputation beyond repute
Default

Quote:
Originally Posted by tukilala View Post
2 bijection(injective and surjective) functions:
1. from (0, 1) to (0,infinite )
2. from (0,1) to [0,infinite)
1. f(x)=\tan \left( \frac{\pi x}{2} \right)
Reply With Quote
The following users thank Plato for this useful post:
Donate to MHF
  #3  
Old July 5th, 2009, 07:29 PM
TheAbstractionist's Avatar
Senior Member
 
Join Date: Apr 2009
Posts: 328
Country:
Thanks: 135
Thanked 158 Times in 138 Posts
TheAbstractionist has a spectacular aura aboutTheAbstractionist has a spectacular aura about
Default

Quote:
Originally Posted by tukilala View Post
2. from (0,1) to [0,infinite)
A bijection g:(0,\,1)\to[0,\,1) is defined by
g(x)\ =\ \left\{\begin{array}{cl}0 & x=\dfrac12\\[7mm]
\dfrac1{n-1} & x=\dfrac1n,\ n\in\mathbb Z,\ n\ge3\\[7mm]
x & \mbox{otherwise}
\end{array}\right.
Define F:[0,\,1)\to[0,\,\infty) by F(0)=0 and F(x)=f(x) for 0<x<1 where f is your bijection in (1). Then the required bijection for (2) is F\circ g.
Reply With Quote
The following users thank TheAbstractionist for this useful post:
Donate to MHF
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off
Forum Jump


All times are GMT -7. The time now is 02:57 PM.


Powered by vBulletin® Version 3.7.3
Copyright ©2000 - 2009, Jelsoft Enterprises Ltd.
SEO by vBSEO 3.2.0 ©2008, Crawlability, Inc.
©2005 - 2009 Math Help Forum


Math Help Forum is a community of maths forums with an emphasis on maths help in all levels of mathematics.
Register to post your math questions or just hang out and try some of our math games or visit the arcade.