# Age of Dinosaurs

The first of the dinosaurs appeared around 231 million years ago, and they dominated earth for more than 135 million years. Homo Sapiens, on the other hand, evolved only around 200 thousand years ago. Here’s a chart to help put this into perspective (click to embiggen):

[Pic courtesy: Wikipedia]

Previous “Sense of Proportion” posts: IIIIIIIVVVI.

Posted in Evolution, Numbers

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# 1729

“Archimedes will be remembered when Aeschylus is forgotten, because languages die and mathematical ideas do not. Immortality may be a silly word, but probably a mathematician has the best chance of whatever it may mean.” — G H Hardy

# Zero = Nirvana?

Zero emerged as a result of spiritual as well as numeral thinking.

[Above: The number 270 from a ninth century inscription in Gwalior, India.]

Posted in India, Numbers

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# Proof Without Words VII

From here (PDF link). Mouse-over the image for a verbal description of the proof.

Also check out Proof Without Words IIIIIIIVV, and VI.

# Proof Without Words VI

Proof that the area of a circle is equal to π × r2.

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Previously on this blog: Proof Without Words I, II, III, IV, and V.

# Happy Pi Day 2013

From this year onwards, in addition to celebrating Pi Day on March 14th, I am going to celebrate Pi Approximation Day on July 22nd (22/7) as well. I can really use an additional day of celebration for my favorite mathematical constant!

By the way, here’s an interesting approximation of π: A nano-century is approximately π seconds long. In other words, if you divide the number of seconds in a century by one billion (nano = 1 billionth), you’ll get a result that’s close to π:

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The comic is from Dinosaur Comic.

Previous posts involving π: 3.14, A Sanskrit Mnemonic for π, Happy Pi Day!, A Mathematical Conundrum.

# Proof Without Words V

Another geometric series followed by a visual proof:

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Previously on this blog: Proof Without Words I, II, III, and IV.

Posted in Numbers

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# Proof Without Words IV

Here’s an infinite geometric series followed by a visual proof:

[Source: Mathematics Magazine, Vol. 62, No. 5]

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Previously on this blog, Proof Without Words I, II, and III.

# The Square Root of 2

The square root of 2 is another one of my favorite irrational numbers. It is equal to the hypotenuse of a right triangle whose sides are equal to 1. Unlike π, e and φ, the irrationality of this number is not very apparent, hence it’s not as popular as some of the other irrational numbers. But I feel that it deserves more popularity as there’s something that we use pretty much every day that involves this fascinating number: the standard size paper.

The ratio of the two sides of an A4 size paper – the standard letter format in many countries including US – equals the square root of 2 (~ 1.41421). Because of this aspect ratio, when you cut the paper in half along its longer side, the resulting halves retain the same ratio.

To understand why the square root of 2 is irrational, we can start by asking the following question: ‘Can it be expressed as a ratio of two whole numbers?’ If the answer to this question is ‘yes’ than it is a rational number which can be expressed as n/m, where both n and m are whole numbers. By squaring both sides and multiplying by m2, we get 2m2=n2. This implies that it is possible to have two identical squares with their sides equal to m, whose total area is identical to a bigger square whose sides are equal to n. A visual proof emerges based on this proposition – check out this link (PDF) if you’re interested in understanding how the irrationality of the square root of 2 can be proven based on this hypothesis.

Let me end this post with a nerdy pick-up line: “You must be the square root of two, because I feel irrational around you.”

# 3.14

Happy Pi Day!

Remember that the “Real Pi Day” will be celebrated on March 14th, 2015 at 9:26:53 AM. These numbers (3/14/15, 9:26:53) correspond with the first 10 digits of pi (3.141592653).

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Previously on this blog: A Sanskrit Mnemonic for π, Happy Pi Day!, A Mathematical Conundrum.