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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C++面向对象程序设计
萨维奇 (Walter Savitch) / 周靖 / 清华大学出版社 / 2003-12 / 59.0
《C++面向对象程序设计》具备良好的编排体系,适合打算涉足编程领域的读者阅读,尤其适合大一学生。它最大的特色是Savitch教授最受欢迎的写作风格,这一风格非常适合初学者,能迅速引导他们开始编程实践。《C++面向对象程序设计》包括全面的习题、项目、编程提示、编程示例、编程陷阱以及有用的小结,以帮助初学者更清楚地了解C++。一起来看看 《C++面向对象程序设计》 这本书的介绍吧!