Followup to Favorite Proof

Results to Favorite Proof:

What's your name/twitter? Name of proof Link to proof somewhere online... Why do you like this proof? Additional testaments of love for this proof Additional testaments of love for this proof ...
@dandersod Euclid's Proof of Infinte Primes link Love proof by contradiction. Simple, powerful, easy to understand. From the book
@sophgermain Why square root of 2 is irrational link It's the first proof i show students and it's simple.
@nik_d_maths Induction for sum of squares link Proof by induction is fun, and this involves enough algebra for students to feel they have done something, while being short enough to use early on I love induction?
@stwwilkinson Uncountability of the real numbers (Cantor) link very simple to explain, yet challenges a lot of intuitive notions about infinity The set up for this proof -- the countability of the rational numbers -- is also mind blowing.
@MrHonner Midline of a Triangle link Elementary, but powerful idea in geometry; several different ways to think about why it's true Great way to demonstrate the power of coordinate geometry for proof Leads to beautiful results like Varignon's Theorem
@Moko58 Product of 2 odd number is an odd number link Even beginners can attempt this proof. this is a great proof.
@mpershan Incompleteness of axioms of arithmetic link It's problably the hardest mathematical idea that I even sort of understand, which is definitely part of why I like it, but the self-referential sentence is brilliant and all sorts of cool things follo wform it.
@mathymcmatherso Geometric Proof of the Pythagorean Theorem link Has a visual and algebraic component that go hand-in-hand. Personally: most convincing and direct proof of pythagorean theorem I've ever seen
@j_lanier There exists an irrational number that when raised to an irrational power results in a rational number. link I like this proof because it is simple; it yields a positive result, rather than a "there exists no..."; and it's concrete but so delightfully non-constructive--we find out that there exists such a thing without having a single example of it! So cheeky. I can't promise that it's my favorite ever, but it's a dang neat proof.
@DanielPearcy Can't pick between irrationality of root(2), infinitely many primes, uncountability of reals Looks like I'm a sucker for proof by contradiction. Funnily enough I don't know many recent (last 100 years) proofs

A pretty common theme: Simplicity in presentation or Visual Component.

<snark>Note: No 2 column geometry proofs are found in this list.</snark>

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More pizza?

From a review of a local pizza place:

Because of the easily laid out website, I could see that getting three 10-inch pizzas ($6 for plain cheese, $7 for pepperoni, and $9 for a house combo “Carcass” pie with sausage, bacon, pepperoni and meatballs) would result in more pizza and easier-to-handle packaging than adding ingredients at $2 a pop to an 18-inch family pie, for a net difference of $1.

More pizza? Including/not including crusts?

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Deadly Nightshade

Our baby is teething and while I was at the pharmacy, I saw a homeopathic remedy for teething babies with the following ingredients:

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Belladonna, aka Deadly Nightshade, has what percentage of alkaloids? 0.0000000000003% or 3 x 10^-13%

Or if we take 1g of “medicine” then there are 3 femtograms, or 3 x 10^-15 grams of belladonna alkaloids. How small is this number?

That’s crazy small.

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Bret Victor’s Learnable Programming

Bret Victor (Inventing on Principle) wrote an excellent essay on Learnable Programming. If you have any interest in how people learn computer programming best, or how people learn in general, then go read it. Now. Shoo. And you probably want to read it on a computer; there are several short videos to accompany the text.

This essay was an immune response, triggered by hearing too many times that Inventing on Principle was “about live coding”, and seeing too many attempts to “teach programming” by adorning a JavaScript editor with badges and mascots.

The gauntlet has been thrown down for the Khan Academy CS program. They just got served.

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Batting Averages Puzzler

From the soon to be retiring Car Talk radio show, a fantastic new baseball puzzler.

RAY: As you might guess, I’m a baseball fan. And now that the season is in its waning days, I thought I’d use this baseball Puzzler I’ve been saving.
There are two rookie players, Bluto and Popeye, who started the season on opening day and made a wager as to which one would have the best batting average at the end of the season.
Well, the last day of the season arrives, and not much is going to change–especially considering that neither one of them is in the starting lineup.
Bluto says, “Hey, Popeye, what did you bat for the first half of the year?”

Popeye answers, “I batted .250.”

And Bluto responds, “Well, I got you there. I batted .300. How about after the All-Star break?”

Proudly, Popeye pipes up, “I batted .375.”
Bluto says, “Pretty good, but I batted .400. Fork over the 20 bucks that we bet.”
The bat boy, Dougie, saunters over and says, “Don’t pay the 20 bucks, Popeye. I think you won.”
TOM: Why is someone who batted .375 not playing in the last game of the season? That’s what I want to know!
RAY: Good point. But the question is this: How could Popeye have won?

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iPads save Jetfuel

From paritynews:

American Airlines has announced that it has received the permission from FAA to allow its pilots to carry and use iPads in the cockpit during “all phases of flight.”

According to the airlines, the tablet will enable pilots to store documentation in electronic form on the iPad which otherwise weighs 15.875 kg (35 pounds) when in printed form. Use of the digital documentation will enable the airlines to save as much as US $1.2 million of fuel each year.

$1.2 million? How much does it take to fly a pound of weight from here to there?

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