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'''Pi''', or '''Archimedes' constant''', is an perhaps the most important [[mathematics|mathematical]] constant 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 16th letter of the Greek alphabet, '''<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