Question 936623
radius(r) = hypotenuse(h) of right isosceles triangle / 2
h^2 = 8^2 + 8^2
h^2 = 64 + 64 = 128
h = square root(128) = 11.31
r = 11.31 / 2 = 5.655
note.  To see how this works imagine a square inscribed in the circle and draw one of the squares diagonals, this gives us two inscribed isosceles right triangles, we need to work with just one of them.