Editing Squaring the circle (section)

=== Constructions using 355/113 ===
{{multiple image
|image1=01 Squaring the circle-Gelder-1849.svg|caption1=Jacob de Gelder's 355/113 construction
|image2=Approximately squaring the circle.svg|caption2=Ramanujan's 355/113 construction
|total_width=600}}
Jacob de Gelder published in 1849 a construction based on the approximation
<math display=block>\pi\approx\frac{355}{113} = 3.141\;592{\color{red}\;920\;\ldots}</math>
This value is accurate to six decimal places and has been known in China since the 5th century as [[Milü]], and in Europe since the 17th century.{{r|hobson}}

Gelder did not construct the side of the square; it was enough for him to find the value 
<math display=block>\overline{AH}= \frac{4^2}{7^2+8^2}.</math>
The illustration shows de Gelder's construction.

In 1914, Indian mathematician [[Srinivasa Ramanujan]] gave another geometric construction for the same approximation.{{r|ramanujan1|ramanujan2}}
{{Clear}}