内容简介:If you think about it, pi is really weird. This irrational number shows up in the craziest places. If you swing a mass back and forth on string,Of course, most people associate pi with circles. That's understandable, since the most basic definition of pi i
If you think about it, pi is really weird. This irrational number shows up in the craziest places. If you swing a mass back and forth on string, there's a pi in there . It pops up in the Heisenberg uncertainty principle , Einstein's general relativity, and the interaction between two electric charges.
Of course, most people associate pi with circles. That's understandable, since the most basic definition of pi is the ratio of the circumference to the diameter of a circle:
Now for the important part. Tomorrow, as you may know, is Pi Day. Why tomorrow? Because it’s March 14—yes, 3/14—and 3.14 is the value of pi to two decimals. Of course, the actual number continues to an infinite number of decimal places: 3.14159265359 … and so on forever. That’s why it’s called irrational.
I should add that the US is pretty much the only place that uses the middle-endian date format of month/day/year. If you go with the little-endian format of day/month/year, then today is 14/3—which is obviously not pi. (In that case I suggest July 22, since the fraction 7/22 is a fairly decent approximation for pi.)
Anyway, my traditional way of celebrating Pi Day is to find a new way each year of calculating a numerical value for pi. It's just what I do. I've been at this for quite some time now, so here are some of my favorites:
- Finding piusing random numbers (and Python)
- Determining the value of pi using a mass oscillating on a spring
- Actually measuring the circumference and diameter of real circles
I have even more Pi Day posts here . But now let's try this a new way. Let’s see how close we can get to pi by drawing a circle.
Here's how this will work. You draw a circle. From that circle, you can determine both the circumference and the radius. Then the value of pi would be the circumference divided by twice the radius. Simple, right?
Oh, but what if your circle isn't perfect? I mean, who draws perfect circles anyway? Let's imagine that this un-perfect circle is actually a bunch of discrete points connected by line segments. If you zoomed on a part of it, it might look like this:
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Google是如何控制世界的
(美)丹尼尔·伊克比亚 / 李军 / 东方出版社 / 2008-08 / 36.00元
秘Google的发展之路! Google,这个有着数百亿的网页存储量、每天两亿搜索次数的搜索引擎,最初仅仅是一个方程式。这个由拉里·佩奇和塞吉·布林两位天才创造出的超级算法甚至比可口可乐的配方还要保密。 当广告公司为自己网页在搜索结果中的排序争得头破血流时,Google正悠然地坐收渔翁之利,这种天才的拍卖广告链接的商业模式给Google带来了令人瞠目结舌的企业利润!仅仅从1999~20......一起来看看 《Google是如何控制世界的》 这本书的介绍吧!