## 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 :-) |

# An irrational "aha!" puzzle

### #1

Posted 24 September 2013 - 04:33 AM

Brute force or computer simulations are often brought to bear on mathematical problems. Among the motivation for using these approaches is they can obviate the need for careful thought. But careful thought often shows a simpler path to the answer. Occasionally, by argument from analogy to already solved problems, or invoking properties of the type of expression, for example, that the answer must possess, a solution can be found without seemingly solving the puzzle at all. Or, if an equation must be solved, it's one much simpler than first thought. Some people refer to these solutions as coming to them in what they call "Aha!" moments.

I will post a series of "Aha!" puzzles, starting with a rather easy one.

The Golden Ratio * g* has a number of definitions. The one that provides the best clue to our answer is to note that a rectangle of dimensions

*x 1 has the property that if it is cut into a square and another rectangle, the second rectangle has the same proportions as the first.*

**g**

Prove that * g* is irrational.

I know its usual symbol is Greek phi; but I don't know how to make one here.

*Vidi vici veni.*

### #2

Posted 24 September 2013 - 12:01 PM

### #3

Posted 24 September 2013 - 03:01 PM

Perfect. That is a proof. And even tho not all square roots are irrational this one is.

Spoiler for trial

Now, I'm looking for a proof that begins with the assumption that

**is rational and show that it leads to an impossible result.**

*g**Vidi vici veni.*

### #4

Posted 24 September 2013 - 06:53 PM

### #5

Posted 25 September 2013 - 09:49 AM

### #6

Posted 28 September 2013 - 06:34 PM

**Edited by ThunderCloud, 28 September 2013 - 06:38 PM.**

### #7

Posted 10 October 2013 - 12:28 PM Best Answer

*Vidi vici veni.*

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

0 members, 0 guests, 0 anonymous users