Distinguish between regular and irregular polygons based on reasoning about equal sides and equal angles
Look at a stop sign: its eight sides all match, and so do its eight corners. A polygon is a flat shape with straight sides. It is regular when every side is the same length and every angle is the same size. If even one side or angle is different, the polygon is irregular.
A square has 4 equal sides and 4 right angles, so it is regular. A rectangle also has 4 right angles, but two sides are longer than the other two, so most rectangles are irregular. The number of sides never decides it. A triangle with 3 matching sides and 3 matching angles is regular, and so is an octagon, a polygon with 8 sides, when all 8 sides and all 8 angles match.
When you check a polygon, look at the sides first, then the angles. Both have to match for the shape to be regular. If either one is off, the polygon is irregular.
Regular polygons have every side and every angle matching; if sides or angles differ, the polygon is irregular.
The school is building a new play area, and Mia has the plan on paper. The ground gets covered in paving slabs. The first slab is a rectangle, 60 cm along the top and 40 cm down the side. You have worked with rectangle sides and corners before: every corner is a right angle.
Is that rectangle slab a regular polygon?
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