3.14 Day

[Ray in La Mesa]

My step daughter is a math teacher & told me today is pi day, enjoy it with whatever pie you like.

[California Travieso]

Originally Posted by Ray in La Mesa

My step daughter is a math teacher & told me today is pi day, enjoy it with whatever pie you like.

I would like to enjoy it, but sadly they closed our Polly’s Pie Shop here in Moreno Vally last week. They could have waited until after Pi day.

David Serrano

[Joe K]

Area of a circle PiR2 (pie R squared)

No - pie are round - cornbread are square.

Joe K

[Elmo Rodge]

pi are 3,14159265358979323846. How do I know this? It's my birthday. 78 is just a fond memory.
Wayno

[Chris in WNC]

Originally Posted by Joe K

Area of a circle PiR2 (pie R squared)

No - pie are round - cornbread are square.

Joe K

Joe, I make my cornbread in an iron skillet so my cornbread are round.....

[atch]

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Many years ago there was a restaurant here in Columbia, Missouri owned by "Poor Ken" and "Lonesome Del". They made their own tv commercials using a blackboard and chalk with "pi r squared" (the actual mathematical symbols) written on the board. One would say "pi r squared". The other would say "no, pie are round". Then "pi r square". Then "no, pie r round". This went on three or four times then one miraculously had a pie in his hand and said "pie r messy" as he hit the other one in the face with the pie. They made many of these commercials but the wording and the pie-in-the-face were always there.

[Joe K]

Originally Posted by Chris in WNC

Joe, I make my cornbread in an iron skillet so my cornbread are round.....

We took on the Cornbread are square phrase in College Pre-Calc math, but I think it originally was part of a "Hee-Haw" routine.

Looking up the phrase on the Internet it seems a southern/appalachian colloquialism.

Joe K

[nkaminar]

314 trillion digits of pi was just calculated on a single Dell PowerEdge R7725 server that ran constantly for nearly four months. See https://www.livescience.com/physics-...ely-irrational

For most engineering calculations only 4 decimal places are needed.

[Joe K]

Originally Posted by nkaminar

314 trillion digits of pi was just calculated on a single Dell PowerEdge R7725 server that ran constantly for nearly four months. See https://www.livescience.com/physics-...ely-irrational

For most engineering calculations only 4 decimal places are needed.

One of the entry level engineering course examples involved the "engineering effect" that "significant digits" has on the final outcome.

To demonstrate this, the Professor calculated some common engineering calculation (I think it volumetric compression in a cylinder) and instead of Pi used to calculate the area, he used "3." Surprisingly, it didn't make that much difference in the answer, actually less than the 3.14/3 fraction/percentage (4.06 percent) that starting with the incorrect value represented.

It became our task for that evening to identify why this was so. Which meant doing the calculation "in parallel" for each step and comparing the intermediate answers all the way down to the end.

Joe K

[JayJay]

Originally Posted by nkaminar

314 trillion digits of pi was just calculated on a single Dell PowerEdge R7725 server that ran constantly for nearly four months. See https://www.livescience.com/physics-...ely-irrational

For most engineering calculations only 4 decimal places are needed.

I cheat - all of my calculators have a "pi" key, which I presume is accurate to several decimal places more than 4. Although I agree, a fifth decimal place would only affect the final result to a factor of 0.0032%.

[atch]

113/355 is close enough for 99.99% of calculations. Divide it out on your calculator and compare.

EDIT: I have the numbers reversed. it's 355/113.

[atch]

And 113355 isn't very hard to remember. If it was I couldn't remember it. First 3 odd numbers.

[CT Jack]

Archimedes also proved that the ratio of the area of a circle to the square of its radius is equal to PI (A/r square = PI)

[Trapdoor2]

I always used 22/7...

3.17 is more important...'cause that's my birthday.

I've eaten a lot of green birthday cake.

[Mike1291]

In the 2010s when I was in college, all of the math professors told us to use 3.14 for pi and that any additional significant digits were unnecessary. On one occasion I used nine significant digits on a quiz and the professor got mad at me and told me to never do it again! It was either from that or from the times I'd hand write how I think I needed to finish the problem but didn't know how to

[updraught]

It was 14.3 here and Right Hand Drive on the left of the road, the water spun clockwise down the drain and the cheese was yellow.

[California Travieso]

When I was in college in the late 1950’s, we used slide rules that were accurate to two significant figures, so 3.14 for Pi was adequate.

David Serrano

[JayJay]

Originally Posted by atch

113/355 is close enough for 99.99% of calculations. Divide it out on your calculator and compare.

I think you mean 355/113, don’t you? Or 1/(113/355)?

[nkaminar]

No calculation of Pi is correct, even the ones with trillions of decimal places are approximations. Pi is an irrational number.

The more accurate approximations are only important in things like calculating the curvature of space-time.

The first calculations of Pi were done by calculating the total length of the sides of a polygon and continuing to increase the number of sides until it was almost round.

Several algorithms have been developed for calculating Pi, see https://en.wikipedia.org/wiki/Approximations_of_pi

You calculator stores a value of Pi instead of calculating it each time. That saves time when doing work on the calculator.


355/113 is accurate to the 7th decimal.

[JayJay]

Originally Posted by California Travieso

When I was in college in the late 1950’s, we used slide rules that were accurate to two significant figures, so 3.14 for Pi was adequate.

David Serrano

I went through school in the early ‘70s, just at the transition between slide rules and calculators. My dad’s high school graduation present to me was lunch then a trip to the K&E dealer in San Francisco to pick out a new bamboo log-log slide rule for college. He went to engineering school in the late ‘30s. Even into the 80s he would run a set of numbers on a calculator, then whip out his slide rule to check himself. I still have his slide rule (although mine, regrettably, has been lost to posterity).

We weren’t allowed to use calculators on exams when I was in school. Something about they were considered “elitist”. Gotta love that California thinking, even 50+ years ago.

My “go to” calculator is the HP 15C, both “hard copy” and app emulator.