square inside square...serkel radius=8
that meen OUTSIDE serkel
square=regular polygon with 4 sides
outside serkel radius=0.7071068* length av polygon side
thus, polygon side leng=8/0.7071068
=11.3137082
in jenral, outside radius=(1/2)*(poly side leng) /koside(beta)
beta=(180-alfa)/2
alfa=360 deg/(number sides)