<P> In Measurement of a Circle written circa 250 BCE , Archimedes showed that this ratio ( C / d , since he did not use the name π ) was greater than 310 / 71 but less than 31 / 7 by calculating the perimeters of an inscribed and a circumscribed regular polygon of 96 sides . This method for approximating π was used for centuries , obtaining more accuracy by using polygons of larger and larger number of sides . The last such calculation was performed in 1630 by Christoph Grienberger who used polygons with 10 sides . </P>
<P> In Measurement of a Circle written circa 250 BCE , Archimedes showed that this ratio ( C / d , since he did not use the name π ) was greater than 310 / 71 but less than 31 / 7 by calculating the perimeters of an inscribed and a circumscribed regular polygon of 96 sides . This method for approximating π was used for centuries , obtaining more accuracy by using polygons of larger and larger number of sides . The last such calculation was performed in 1630 by Christoph Grienberger who used polygons with 10 sides . </P>
who discovered the formula for the circumference of a circle
who discovered the formula for the circumference of a circle
Archimedes
Archimedes