The radius of the circle = circumference / (2 * PI)
radius = 50 /
6.2831853072 cm
radius =
7.9577471546 cm
Two radii of the circle plus the side of the square form a 45 45 90 triangle.
The side of the square = radius * sq root (2)
The side of the square =
7.9577471546 * 1.4142135624
The side of the square = 11.25 cm