The side of the ABSD square is 3 cm. Calculate the perimeter, area, diagonal and inscribed radius of this square.

Find the perimeter of the square:
P = 4 * a = 4 * 3 = 12 (cm).
We find the area of a square using the formula:
S = a * a = a² = 3² = 9 (cm²).
By the Pythagorean theorem, we find the diagonal of the square. It is the hypotenuse in a right-angled triangle, in which the legs are the sides of this square.
d = √ (a² + a²) = √18 = 3√2 (cm).
The radius of the inscribed circle is found by the formula:
r = a / 2 = 3/2 = 1.5 (cm).
Answer: perimeter 12 cm, area 9 cm², diagonal 3√2 cm, inscribed circle radius 1.5 cm.