problem :

dependence between area of circle to area of square around this circle ( 2 * ray of circle is side of square ) is 2 / pi, however the dependence of sector of this square ( quarter ) to sector of this circle ( quarter ) made on the ray of circle isnt correct with

2 / pi

r^2 / ( pi * r^2 / 4 ) != (nie równa się) 2 / pi