en.wikipedia.org/wiki/Pi

The number π is a mathematical constant. Originally defined as the ratio of a
circle's ... The symbol **used** by mathematicians to represent the ratio of a circle's ...

www.livescience.com/29197-what-is-pi.html

Apr 30, 2013 **...** **Pi** (π), the 16th letter of the Greek alphabet, is **used** to represent the most widely
known mathematical constant. By definition, **pi** is the ratio of the ...

www.angio.net/pi/whypi.html

Archimedes **used** this trick with 96 sided polygons to correctly estimate **Pi** to
about two digits (3.14), proving 3.1408 < **Pi** < 3.1428. You can try this trick with ...

curtiscenter.math.ucla.edu/content/pi_applications

Dr. David H. Bailey, co-discoverer of the Bailey–Borwein–Plouffe formula for **pi**,
guest authored this post. Many presume that π is only **used for** geometric ...

mathforum.org/dr.math/faq/faq.pi.html

**What is Pi**? Who first **used Pi**? How do you find it? What is it for? How many digits
is it?

www.newyorker.com/tech/elements/pi-day-why-pi-matters

Mar 13, 2015 **...** They're calling this the **Pi** Day of the century: 3.14.15. ... memorized these and
similar formulas for the S.A.T.s and then never again **used** them, ...

www.dkfindout.com/us/math/numbers/pi

**Pi** is a useful number that is **used** in mathematical formulas. It is also written as
the π symbol. The number **pi** is usually written as 3.14. This has been rounded to
...

www.scientificamerican.com/article/what-is-pi-and-how-did-it

According to Petr Beckmann's A History of **Pi**, the Greek letter was first **used for**
this purpose by William Jones in 1706, probably as an abbreviation of periphery,
...

www.mathsisfun.com/numbers/pi.html

**Pi** (π). **pi** circle diameter. Draw a circle with a diameter (all the way across the
circle) ... There are many special methods **used** to calculate π and here is one
you ...