Find the area of the biggest possible square that would fit into a circle having a radius of 3cm.

The largest square that can fit in a square of radius 3cm can have its diagonal length twice its radius.

But diagonal of a square is root square root of {2} x length of each side.

Hence from above, diagonal length is 6 cm and so, the side can be 3 * (2^1/2)

So area of square is (3 * (2^1/2)) ^2 = 18 cm^2