area of square

c: diagonal
a, b: sides of square

c^2=a^2+b^2=a^2+a^2=2a^2
a = sqrt(200cm^2)
c=sqrt( 2*sqrt(200)^2 )
[input]sqrt( 2*sqrt(200)^2 )[/input]
c=sqrt( 2*200 )
[input]sqrt( 2*200 )[/input]