Big rectangle, small rectangle, big cube, small cube, big cuboid, middle cuboid, small cuboid, big cylinder, small cylinder, big circle, small circle and triangle are divided into big, medium and small.

Decision theorem

1: A diamond with equal diagonal lines is a square.

2. Diamonds with right angles are squares.

3: Rectangles with diagonal lines perpendicular to each other are squares.

4. A set of rectangles with equal adjacent sides is a square.

5. A set of parallelograms with equal adjacent sides and one angle at right angles is a square.

Reference to the above content: Baidu Encyclopedia-Plaza