# IntMath Newsletter: Golden spiral, $0 math e-books, CDF format

By Murray Bourne, 05 Sep 2011

5 Sep 2011

In this Newsletter:

1. Golden Spiral

2. Math e-Books for $0

3. 13 yr-old designs efficient solar collectors using Fibonacci and trees

4. Wolfram's new Computable Document Format

5. Math Puzzle: Solution and new one

6. Friday math movies

7. Final thought: Powerful weapon

## 1. Golden Spiral

**Suitable for: **This is an interesting article because there are several important math concepts involved. If you have some basic understanding of trigonometry and exponentials you will get more out of it.

Golden Spirals involve a lot of interesting math, from exponential curves to polar coordinates, tangents to a curve and approximating curves. |

## 2. Math e-Books for $0

**Suitable for: **Everyone who likes a freebie!

Here's a collection of free (or cheap), mostly good quality math text books in PDF format. |

## 3. 13 yr-old designs efficient solar collectors using Fibonacci sequence and trees

**Suitable for: **Everyone.

This is a useful discovery by a 13 yr-old, using math and good observation skills. Trouble is, it turned out to be not as efficient as claimed! (See the comments.) 13 yr-old designs efficient solar collectors using Fibonacci sequence and trees |

## 4. Wolfram's new Computable Document Format and Online Conference

We've had PDF format for some time now.

Wolfram, developers of Mathematica and the brilliant Wolfram|Alpha, have released a new type of document which can include interactive animations of math concepts.

The documents it produces are free, but you need to purchase Mathematica if you want to produce such documents. But never mind, there's still a lot of value in this. You'll need to download a small file in order to view, and play with, the CDF files.

Interactive Whiteboard users - this is for you!

Go to Computable Document Format

**Wolfram Mathematica Online Conference**

Wolfram is also hosting a free Mathematica Virtual Conference on Sep 26th (for US time zone) and on 27th Sep (Europe time zone - also good for Asia).

For those new to Mathematica, the "Discover Mathematica" session will be good. There's also a session on "Applying Mathematica in Industry and Research" and for the teachers, "Applying Mathematica in Education".

I'll be attending the 27th Sep session - say hello if you see my name in the participant list!

Information and free registration: Wolfram Mathematica Virtual Conference 2011

## 5. Math Puzzle - solution and new one

Last newsletter, the math puzzle was:

If the end of the world should come on the first day of a new century, what is the probability that it will happen on a Sunday?

While it seems the probability should be 1/7, it isn't!

The first day of a century can never fall on a Sunday; nor on a Wednesday or a Friday. See here for an explanation.

**New puzzle: **

A business man works on the 10th floor of an office building and always takes the elevator down to ground level at the end of the day.

Yet every morning he only takes the elevator to the 7th floor and walks up the stairs to the 10th floor, even when he is in a hurry.

Why? (You can answer here.)

## 6. Friday math movies

I have a back-log of math movies this Newsletter. Enjoy!

## (a) Miss USA 2011 - Should math be taught in schools?
This is hilarious - or very disturbing - depending on your point of view. Friday math movie: Miss USA 2011 - Should math be taught in schools? |

## (b) Wireless data from every light bulb
Here's a great idea - get your wireless data more efficiently and safely. |

## (c) How algorithms shape our world
Done a Google search today? You've used an algorithm that is helping to change the world. |

## 6. Final thought – powerful weapon

Sadly, a lot of students (and some teachers!) mope around complaining about how everything "sucks" and is "sooo boring". But the world is full of so many great and interesting things - we only have to look - and enjoy!

Ferdinand Foch, French soldier and military theorist of the late 19th century, could have been talking to jaded students when he said:

The most powerful weapon on earth is the human soul on fire.

[Ferdinand Foch]

Until next time, enjoy whatever you learn.

See the 12 Comments below.

6 Sep 2011 at 12:48 am [Comment permalink]

He is only tall enough to reach the button of 7th floor.

6 Sep 2011 at 12:49 am [Comment permalink]

He is a midget.

6 Sep 2011 at 2:59 am [Comment permalink]

Our subject is vertically challenged - he can only reach as high as the button for the seventh floor.

6 Sep 2011 at 3:21 am [Comment permalink]

There is no elevator between the 7th and 10th floors. At the end of the day he also has to walk from the 10th floor to the 7th floor to catch the elevator down to the ground floor. There was no mention that he could catch the elevator down from the 10th floor.

6 Sep 2011 at 8:21 am [Comment permalink]

He is too short to reach the 10th floor button!

6 Sep 2011 at 2:25 pm [Comment permalink]

Answer to elevator puzzle:

He's too short to reach the button for the tenth floor. Buttons are arranged vertically from 10 to 1

10 Sep 2011 at 6:25 am [Comment permalink]

Mr shorty!

11 Sep 2011 at 6:25 pm [Comment permalink]

How exactly do you download a book from say Google eBooks?

11 Sep 2011 at 6:40 pm [Comment permalink]

@Peter: There are 3 possible situations in Google Books:

(1) The book is in the public domain (out of copyright, and usually old), and you can view all of the book in Google Books and can download it in a variety of formats (eg Here is Treasure Island in available formats). PDF is the simplest for desktop or laptop computers.

(2) The book is copyrighted, but the publishers have given permission for Google to display "some" pages (although I usually find they show "most" pages). There is no download link, but links to the publishers (fair enough, they own the rights)

(3) There is strict copyright, and Google only provides information about the book, and you can't view any of it except maybe a few "snippet" sentences.

Hope that helps!

12 Sep 2011 at 8:03 pm [Comment permalink]

wow the answers here are quite logical, I feel bad for not thinking this way....... but no matter, i want to ask; if the problem was really his height don't you think he would have found a way to overcome it by tagging along with someone who works on the same floor as he does? hence this question won't even exist in the first place. so I'm thinking it's something else, I was thinking he collects the day's newspaper every morning on the 7th floor and decides to walk the rest may be cos the elevator is busy or something.....Of course I'm not debunking anyone's answer since I'm the only one with a different answer here. So can anyone explain to me what i asked initially?

13 Sep 2011 at 2:46 am [Comment permalink]

"Yet every morning he only takes the elevator to the 7th floor and walks up the stairs to the 10th floor, even when he is in a hurry."

By this statement I would gather that if he had some sort of alternate method available (i.e. by "tagging along with someone who works on the same floor as he does") he would avail himself of this at least on occasions where he was in a hurry. This leads me to the (rather presumptuous, admittedly) conclusion that he has no other available method, except the one that limits him somewhat.

21 Sep 2011 at 7:44 pm [Comment permalink]

thanx jordan