Q1
What is a polygon?
AA closed shape with straight sides
BA curved shape
CAn open shape
DA 3D shape
ICSEClass 8 (ICSE)MathematicsCh 16 · Topic 1
Understanding Shapes (Polygons)
Polygons are closed shapes with straight sides, classified by their number of sides, and follow specific angle sum properties.
Core concept
A polygon's angle sum can be calculated using the formula (n-2) × 180°, where n is the number of sides.
How it works
For a quadrilateral (4 sides), the angle sum is (4-2)×180° = 360°, while a pentagon (5 sides) has (5-2)×180° = 540°.
Why it matters
Regular polygons have all sides and angles equal, like an equilateral triangle or a square, while irregular polygons do not.
Key detail
Understanding polygon properties helps us classify shapes and solve geometry problems involving angles and sides.
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Quick notes
• A polygon is a closed shape with straight sides.
• Angle sum formula: (n-2) × 180°.
• Quadrilateral angle sum: 360°.
• Pentagon angle sum: 540°.
• Regular polygons have equal sides and angles.
• Irregular polygons do not.
• Polygon properties help classify shapes.
• They help solve angle and side problems.