Teacher2Teacher 
Q&A #6013 
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From: Loyd To: Teacher2Teacher Public Discussion Date: 2006111416:15:50 Subject: Re: PI I know you asked for uses not demonstrations. I used a bicycle wheel and marked it with chaulk at the bottom and marked the floor at the same time. Then you roll the wheel across the room until the mark is on the floor again. It is easy to measure the distance rolled. Of course the distance rolled divided by the diameter will get you close to the value of PI. "Good enought for government work" as government workers used to say just for fun. In the past when I wrote computer programs, I used the first three double odd digits to get PI. 11 33 55 are the three double odd digits. Place a divide symbol thus: 355/113 and you get PI to about 6 places. If a student is working at a computer, he can go to Accessories, click on calculator then click on view and click "scientific". 3.1415926535897932384626433832795 is the value you will find. Not bad accuracy. Compare that to 355 divided by 113. Of course you will find pi in any geometry, trig and engineering books where rotation or circular shapes are involved. The voltage out of your wall sockets are the result of rotating machinry so these waveforms can be expressed using PI. In engineering, radians are most often used rather than degrees so the conversion from degrees to radians results in PI/2 radians being equal to 90 degrees. Electric fields are the result of rotation and there are a large number of formulas in any scientific works where PI is used. A scientific calculator is valuable when working with radians because both radians and degrees can be selected. My father always said, "Pie are square not round." By that saying he always remembered the formula for the area of a circle. My father told a story about a congressman in the 1800s who wanted to change the value of PI to 3 in order to simplify the math. Of course, the didn't get that bill through congress.
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