# Happy Phi Day!

In the United States, today is abbreviated 1/6/18, matching the first four significant digits of the irrational number $\phi = (1 + \sqrt{5})/2$, otherwise known as the golden ratio. For a good introduction to $\phi$, see http://www.foxnews.com/story/2007/06/18/happy-phi-day-perfect-time-for-some-phinancial-fun.html.

For today, I’ll give a fun fact that I learned last year; for its national flag, the country of Togo chose a rectangle whose dimensions matches the golden ratio.

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