Let side of square be a
by applying Pythagoras theorem
a^2+a^2= 12^2 (both length and breadth are same because it is a square)
2a^2 = 12^2
a^2= 12^2/root2
a = 12/root2
a = 6root2
By using Pythagoras theorm!
Length of one side of circle is 6√2
So area of Circle is 6√2*6√2
=72 cm²