For a square inscribed in a circle, the diagonal of the square equals the diameter of the circle.
Using the Pythagorean relationship for a square:
genui{"geometry_measurement_learning_block":{"type_id":"PYTHAGOREAN_THEOREM"}}
If the side of the square is (s), then:
s2=16
s=216=82 cm
Area of the square:
s2=(82)2=64×2=128 cm2