# PI DAY 2018!

Happy pi day!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Pi Day as a holiday is 30 years old this year (unless someone had been celebrating quietly on 3/14’s before Larry Shaw publicly founded Pi Day at the San Francisco Exploratorium in 1988)!

While last year was a pi day snow day for us, this year the snow has mostly missed us in Maryland, while Boston area folks have had several huge storms in a row, and some of them do have a pi day snow day today!

The day was off to a good start this morning with a beautiful pi day sunrise:

I was up early to buy some pies, as per usual, when I stumbled across a pi-day pie sale! While I’ve seen photos of these before on social media, this is the first time I’ve actually come across one in person on a pi day myself!

I made my chalkboard a little busier than usual, including a few extra pi facts:

I also wore a new pi tie today (some years I’ve worn pi t-shirts). You can’t tell from the photo, but the image/pattern is made up of pi’s digits!

My first period AP CS A (Java / object-oriented programming class, with juniors and seniors) is the only class I did a pi-focused lesson with this year. In my other classes, we took a ten-minute pi and pie break, and talked about pi facts while eating, then back to our regularly-scheduled lesson. But in AP CS A, we coded an infinite series for pi in Java. We used the Leibniz formula, relatively easy to understand and code: 1/1 – 1/3 + 1/5 – 1/7 + 1/9 – 1/11 + 1/13 – …

This actually converges fairly slowly, compared to other infinite series for pi. Here are the results after ten terms, with the terms included on the left, and the running summation on the right of each line:

Here we are after 1000 iterations, just the sums:

And after a million terms, we’re getting pi accurate to five digits:

A million terms took a few minutes to run, so we didn’t dare try ten million, for fear we would break our ancient computers! Nor did we try to break the record of 22 trillion digits of pi, which would need many many times more terms if we were to use this series 🙂

Also today, in other news, a nationwide walkout against gun violence, which students at my school participated in as well. And I took two students on a field trip; the students had built a custom-engineered bicycle for a kid with a disability last month during National Engineering Week, and today we got to deliver the bike to the kid and his mother. So that was pretty cool.

Anyway, that’s how my day went, hope your pi day was similarly awesome!

Here’s my round-up of a few Pi Links:

And a few really creative pi-related photos, found via Twitter (linked to their sources):

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