A square is composed of one face. It is one of the special parallelograms. That is, a parallelogram with a set of equal adjacent sides and a right angle is called a square or a regular quadrilateral. Square has all the characteristics of rectangle and diamond.
Decision theorem:
1. A diamond with equal diagonals is a square.
2. A diamond with a right angle is a square.
3. A rectangle whose diagonals are perpendicular to each other is a square.
4. A group of rectangles with equal adjacent sides is a square.
5. A set of parallelograms with equal adjacent sides and a right angle is a square.
6. A parallelogram whose diagonals are perpendicular and equal to each other is a square.
7. A square is a quadrilateral whose diagonals are equal and perpendicular to each other.
8. A quadrilateral whose adjacent sides are equal and whose three corners are right angles is a square.
9. A quadrilateral that is both a diamond and a rectangle is a square.