## Welcome to BrainDen.com - Brain Teasers Forum

 Welcome to BrainDen.com - Brain Teasers Forum. Like most online communities you must register to post in our community, but don't worry this is a simple free process. To be a part of BrainDen Forums you may create a new account or sign in if you already have an account. As a member you could start new topics, reply to others, subscribe to topics/forums to get automatic updates, get your own profile and make new friends. Of course, you can also enjoy our collection of amazing optical illusions and cool math games. If you like our site, you may support us by simply clicking Google "+1" or Facebook "Like" buttons at the top. If you have a website, we would appreciate a little link to BrainDen. Thanks and enjoy the Den :-)
Guest Message by DevFuse

# Ridiculous Inverse

5 replies to this topic

Senior Member

• Members
• 1828 posts
• Gender:Female

Posted 20 May 2013 - 07:04 PM

Many of my algebra and precalculus students think the 'inverse function' of f(x), often written f^(-1)(x), is the same as the reciprocal 1/f(x) (mistaking the -1 for an exponent).  This (as I am obliged to remind them) is almost always false. But can you find at least one function whose inverse is also its reciprocal? Tiebreaker: Find as many as you can!

• 0

### #2 kingofpain

kingofpain

• Members
• 354 posts
• Gender:Male

Posted 22 May 2013 - 06:25 PM

Spoiler for hmmm...

• 0

### #3 bonanova

bonanova

bonanova

• Moderator
• 6148 posts
• Gender:Male
• Location:New York

Posted 23 May 2013 - 11:56 AM

There are a few functions that are their own inverses. 1/x (away from 0) is one instance.
For tiebreaker are you asking for other instances of functions for which f[f(x)]= x?
Or for more functions whose inverses are their reciprocals?
• 0

Vidi vici veni.

Senior Member

• Members
• 1828 posts
• Gender:Female

Posted 23 May 2013 - 12:36 PM

There are a few functions that are their own inverses. 1/x (away from 0) is one instance.
For tiebreaker are you asking for other instances of functions for which f[f(x)]= x?
Or for more functions whose inverses are their reciprocals?

The latter
• 0

### #5 kingofpain

kingofpain

• Members
• 354 posts
• Gender:Male

Posted 23 May 2013 - 06:57 PM

Spoiler for unbroken ties...

• 0

### #6 James33

James33

Junior Member

• Members
• 38 posts

Posted 23 May 2013 - 07:19 PM

Spoiler for unbroken ties...

I think the OP means that f^-1(x)=1/f(x).

Spoiler for

• 0

#### 0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users