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'''Pi''', or '''[[Archimedes]]' constant''', is perhaps the most important number in all of [[mathematics]] and engineering.  It is defined as the [[ratio]] of the [[circumference]] of a [[circle]] to its [[diameter]], and represented by the Greek letter '''<big><math>\pi</math></big>'''.  It was first used with its current meaning in 1706 by a Welsh mathematician William Jones,<ref name="hist">{{cite web

'''Pi''', or '''[[Archimedes]]' constant''', is perhaps the most important number in all of [[mathematics]] and engineering.  It is defined as the [[ratio]] of the [[circumference]] of a [[circle]] to its [[diameter]], and represented by the Greek letter '''<big><math>\pi</math></big>'''.  It was first used with its current meaning in 1706 by a Welsh mathematician, William Jones,<ref name="hist">{{cite web

| url = http://www-groups.dcs.st-and.ac.uk/history/HistTopics/Pi_through_the_ages.html  

| url = http://www-groups.dcs.st-and.ac.uk/history/HistTopics/Pi_through_the_ages.html  

| title = A history or Pi

| title = A history or Pi