Shape Detectives: Exploring 2D Shapes

Look around the room you are in right now. Can you spot any flat shapes? A window might be a rectangle. A clock face might be a circle. These flat shapes are called 2D shapes. The '2D' stands for two-dimensional, which means they have width and height but no thickness — like a drawing on paper. Today you are going to become a shape detective and discover what makes each 2D shape special.

Every 2D shape has sides and vertices. A side is a straight line that forms part of the edge of a shape. A vertex is a corner — the point where two sides meet. The plural of vertex is vertices. Let's meet five important 2D shapes: • Triangle — 3 sides, 3 vertices. An equilateral triangle has all 3 sides the same length. • Square — 4 sides, 4 vertices. All 4 sides are equal, and all 4 corners are right angles. A right angle is a perfectly square corner, like the corner of a book. • Rectangle — 4 sides, 4 vertices. Opposite sides are equal, and all 4 corners are right angles. A square is a special type of rectangle. • Pentagon — 5 sides, 5 vertices. • Hexagon — 6 sides, 6 vertices. A regular hexagon has all 6 sides the same length. A shape is called regular when all its sides are equal AND all its angles are equal. A shape is irregular when its sides or angles are different sizes. Worked example: Look at a rectangle with sides of 6 cm, 3 cm, 6 cm, and 3 cm. Count the sides: 1, 2, 3, 4 — so it has 4 sides. Count the vertices: 1, 2, 3, 4 — so it has 4 vertices. Are all sides equal? No — two sides are 6 cm and two are 3 cm, so it is an irregular shape. Do all corners look like the corner of a book? Yes — so it has 4 right angles.