## Wild About Math bloggers 12/17/10

[ The 12/24 Christmas Eve edition of Wild About Math Bloggers! is at Equalis. Here's the 12/17 edition. ]

Fun happenings in the blog world this week. Enjoy.

Robert at Casting Out Nines writes about "Rebuilding the Antikythera Mechanism out of Lego." The Antikythera is an ancient calculator that was used, with striking accuracy, to predict celestial events.

[youtube]http://www.youtube.com/watch?v=RLPVCJjTNgk[/youtube]

If you've not yet discovered Vi Hart's math doodles (or the rest of Vi's site) you're in for a great treat. Vi exemplifies really well how Math can be great fun. Hat tip to Denise at Let's Play Math! and to the Natural Math list. I particularly enjoyed, beyond the doodles, the page on how to cut apples into platonic solids!

Bachelor's Degree has a list of 20 Incredible TED Talks for Math Geeks. Nice!

## Ti-84 Plus Silver Edition giveaway winner

On December 9th I announced a contest to solve a challenge proposed by James Tanton.

STEM skills - science, technology engineering and math - hold the key to tomorrow's innovation. To help students learn tomorrow's job skills, Wild About Math! has teamed-up with Texas Instruments to give away a TI-84 Plus Silver Edition graphing calculator with GraphiTI package. To learn more about TI-84 graphing calculators or other TI products, visit: http://education.ti.com. To learn more about STEM careers, visit: http://education.ti.com/studentzone.

The problem was harder than I thought it would be. I got two submissions and only one was correct. So, I didn't need random.org to tell me who to award the prize to.

Our winner is Daniel Chiquito from North Carolina. Congratulations, Daniel!

Here's a PDF document with Daniel's solution.

I do have one comment on Daniel's solution. It's technically not a formula but an algorithm since it introduces a special case. The Encyclopedia of Integer Sequences (http://oeis.org/A000037), overcomes the issue with this formula:

floor(1/2 *(1 + sqrt(4*n-3)))+ n

I have another TI giveaway contest coming up in January so stay tuned.

## Wild About Math bloggers 12/10/10

[ The 12/17 edition is at Equalis. Here's the 12/10 edition. ]

December 10th is my birthday so today's column is the "Happy Birthday to me" edition. And, in honor of my birthday, I'm running a contest at Wild About Math! where you can win a TI-84 Silver Edition graphing calculator for solving the James Tanton puzzle at the end of this video:

[youtube]http://www.youtube.com/watch?v=GYDtv6nJWOg[/youtube]

Carnival of Mathematics #72 is posted at the 360 Blog.

Here's a great trick performed by David Copperfield based on something called Kruskal's principle. It is the most clever application of this principle I've seen and I've seen a bunch. See Grey Matters and this second post for more on this principle.

[youtube]http://www.youtube.com/watch?v=ZKW244y3peU[/youtube]

## Wild About Math bloggers 12/3/10

[ The 12/10 edition of Wild About Math Bloggers! is at Equalis. Following is last week's edition. ]

Happy December, Everybody! Let's get rolling with this week's Wild About Math Bloggers!

Mathematics and Multimedia Blog Carnival #5 is up at Math Hombre.

The Republic of Mathematics Blog has a nice indirect proof of a problem that James Tanton posted on twitter, that when we round n+sqrt(n), for integer n, we never get a perfect square. And, in his style, James Tanton generalizes the problem:

Round n+sqrt(n) to nearest integer and get the non-square numbers. Round n+sqrt(2n), get non-triangulars. What non-numbers are n+sqrt(3n)?

Thanks, Shecky, for the link to the proof.

## Another TI-84 Plus Silver Edition giveaway puzzle contest!

I've been thoroughly enjoying the books James Tanton sent me, which infuse Math education with life and joy and play, along with the Youtube videos that cover some of the topics in the books. One of his videos particularly intrigued me because it covers a topic I've never run into in my 30+ years of playing with Math. So, I thought I'd invite each of you to watch this particular video, to solve the challenge at the end of the video and, if you're lucky, to win a TI-84 Plus Silver Edition calculator for your efforts.

But first, a word from our sponsor:

STEM skills - science, technology engineering and math - hold the key to tomorrow's innovation. To help students learn tomorrow's job skills, Wild About Math! has teamed-up with Texas Instruments to give away a TI-84 Plus Silver Edition graphing calculator with GraphiTI package. To learn more about TI-84 graphing calculators or other TI products, visit: http://education.ti.com. To learn more about STEM careers, visit: http://education.ti.com/studentzone.

## Spirograph on steroids!

Remember that children's toy that has gears and a hole for a pen that you make cool curved shapes with?

Well, check out this "Three Pendulum Rotary Harmonograph."

[youtube]http://www.youtube.com/watch?v=H4YQonwQUDs[/youtube]

## Wild About Math bloggers 11/26/10

[ The current installment of Wild About Math Bloggers! is at Equalis. Here is last week's episode. ]

I hope you all had a wonderful Thanksgiving Day. Here's this week's roundup.

I'm so in love with James Tanton's work. He recently sent me a half dozen of his books to review. It'll take me time to digest and review them but, in the meantime, let me recommend some of his 90 YouTube videos which I have thoroughly enjoyed which will give you a good feel for his teaching style and for his very fluid way of thinking.

- Twinkle Twinkle and Math. A fun amaze-your-friends kind of thing you can do with something called Kruskal's principle.
- An explanation and a clever application of the Pigeon Hole Principle.
- What does it mean for something to be a 1.6-dimensional object? What does this have to do with fractals?
- Can you turn a hollow rubber ball inside out? How about a donut?
- A proof of Heron's formula for the area of a triangle given only the three sides.

## New James Tanton video on sums of cubes

Have you ever wondered why the sum of the cubes of consecutive positive integers is always a square? The key to one visual proof lies in the humble multiplication table and in an array of square dots.

Here's a new video from James Tanton that shows in a remarkably elegant way that 1^3 + 2^3 + 3^3 + ... + n^3 = (1+2+3+...+n)^2.

And, you don't need to have very much of a background in Math to follow the proof. Absolutely amazing!

[youtube]http://www.youtube.com/watch?v=fKrN2-urUkE[/youtube]