Skill: Identify properties of squares

To identify a square, check its defining properties:

1. It has four sides.
2. All four sides have the same length.
3. All four angles are right angles, measuring $(90^\circ)$.
4. Its opposite sides are parallel.

A square can be turned or tilted and still be a square. Do not decide only by how it looks.

Example

A quadrilateral $(ABCD)$ has these measurements:

• $(AB=5\text{ cm})$
• $(BC=5\text{ cm})$
• $(CD=5\text{ cm})$
• $(DA=5\text{ cm})$
• Each angle measures $(90^\circ)$

Is $(ABCD)$ a square?

Step 1: Count the sides.
The shape has four sides, so it is a quadrilateral.

Step 2: Compare the side lengths.
All four sides measure $(5\text{ cm})$. Thus, all sides are equal.

Step 3: Check the angles.
All four angles measure $(90^\circ)$, so they are right angles.

Step 4: Check opposite sides.
Opposite sides of this shape are parallel.

Because the shape has four equal sides and four right angles, $(ABCD)$ is a square. It is also a rectangle because it has four right angles and a rhombus because it has four equal sides.