Divide the square belt of the elementary school math box by four to get the side length. The formula for calculating the side length of a square is a=√S, which is a special parallelogram, that is, a group of parallelograms with equal adjacent sides and a right angle is called a square, also known as a regular quadrilateral. A square has all the characteristics of a rectangle and a diamond. A diagonal of a square divides the square into two isosceles right triangles, and the included angle between the diagonal and the side is 45. The two diagonal lines of a square divide it into four congruent isosceles right-angled triangles.