How to find ח (phi)

Egypt have found ח value with 3,16. They got it from area of circle equals square of 8/9 times diameter.
We know diameter of circle is the length of the line through the center and touching two points on its edge.
Diameter equals 2R; R is radius of the circle.
Radius is the distance from the center to any point of edge.
The formula becomes:
¬ Area of circle equals square of 8/9 times 2 radiuses,
¬ Area of circle equals 64/81 times 4 radiuses square,
¬ Area of circle equals 3,16 times radiuses square.
We get ח equals 3,16.
Many mathematicians examined carefully about ח with method analytic or use computer till get the value of ח is 3,14.
Now we use the value of ח equals 3,14.