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January 25th, 2019, 08:15 AM  #1 
Newbie Joined: May 2018 From: Idaho, USA Posts: 24 Thanks: 3  Calculating Pi for fun.
Hello, So, I was doing the following equation for fun: (5/2)r^2sin(72) A thought came to my mind I wanted to share. The more sides a regular polygon has, and the smaller the angles, the closer the answer gets to Pi if r=1. I thought this because, the more sides and the smaller the angles, the closer it gets to being a circle. I began to experiment as follows. (5/2)1^2sin(72)=2.377641291 (36/2)1^2sin(10)=3.12566719 (360/2)1^2sin(1)=3.14143315 (3600/2)1^2sin(0.1)=3.14159105 (36000/2)1^2sin(0.01)=3.14159263 (360000/2)1^2sin(0.001)=3.14159265 And so on. When I post this kind of stuff, I am NOT trying to be boastful or smart. I just like sharing what I learn. I just wanted to share this. I hope you enjoyed reading it. If you have anything you want to add on, feel free to do so. Happy calculating! Jared 
January 25th, 2019, 08:37 AM  #2 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,600 Thanks: 2588 Math Focus: Mainly analysis and algebra 
Well done. That's the way Pythagoras (I think) worked out his value for $\pi$. You are in good company.

January 25th, 2019, 09:13 AM  #3  
Senior Member Joined: May 2016 From: USA Posts: 1,306 Thanks: 549  Quote:
EDIT: If I remember correctly, he used inscribed and circumscribed polygons so that he placed upper and lower bounds on the value of pi. Last edited by JeffM1; January 25th, 2019 at 09:15 AM.  
January 25th, 2019, 02:23 PM  #4 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,600 Thanks: 2588 Math Focus: Mainly analysis and algebra 
Close enough! 
January 25th, 2019, 03:58 PM  #5 
Math Team Joined: May 2013 From: The Astral plane Posts: 2,042 Thanks: 815 Math Focus: Wibbly wobbly timeywimey stuff.  
January 25th, 2019, 04:23 PM  #6 
Senior Member Joined: Dec 2015 From: iPhone Posts: 387 Thanks: 61 
Pi is everywhere , i doubt that it hides a lot .
Last edited by idontknow; January 25th, 2019 at 04:26 PM. 

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