Happy Pi Day! We celebrate pi on March 14 because 3-14 gives the first three digits of this famous number. But what’s the big deal about pi anyway? Why does it get a day? Well, for starters, it defines the simplest, most perfect shape, the circle. So it’s everywhere around you. Pi is the ratio of the circumference to the diameter of a circle: π = C/d.
No matter how big or small a circle is, that ratio is always the same. In decimal notation, it’s 3.141592653 … aaand you can run that out as far as you want, because it’s an irrational number, and it never, ever, ever ends.
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