The diagonal of bigger square is 6cm(diameter)

Therefore it's side is 3root2 cm.

Now as the diagonal of smaller square is equal to the side of larger square

There fore the side of smaller square is 3cm

Now

Yellow part =(area of circle-area of larger square)+ area of smaller square

9 pie -18+9

= 9 pie-9

=9(pie-1)

19.26 cm2