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Polygons are 2D shapes with straight sides. Learn names, angle sums, and properties so you can classify shapes and solve perimeter and interior angle problems in KS3 Maths.
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Fascinating Fact:
You can find the sum of the interior angles using (n − 2) × 180°, so a pentagon with 5 sides has (5 − 2) × 180° = 540°.
In KS3 Maths, you study polygons by their sides and angles. You’ll calculate interior and exterior angles, spot regular polygons, and apply properties to solve construction and geometry problems.
Key Terms
Polygon: A 2D shape made from straight line segments joined end to end.
Regular polygon: A polygon with all sides equal and all angles equal.
Interior angle: The angle formed inside a polygon at each vertex.
Frequently Asked Questions (Click to see answers)
How do you find the sum of interior angles of an n-sided polygon?
The sum of interior angles is (n − 2) × 180°. For example, a heptagon (n = 7) has (7 − 2) × 180° = 900°.
What is the exterior angle of a regular polygon?
For a regular polygon, each exterior angle equals 360° ÷ n. If the exterior angle is 30°, then n = 360° ÷ 30° = 12 sides.
How are polygons named by the number of sides?
3: triangle, 4: quadrilateral, 5: pentagon, 6: hexagon, 7: heptagon, 8: octagon, 10: decagon. Add “regular” if all sides and angles are equal.