Study Notes
Polygons are shapes with straight sides. They can be classified based on the number of sides and angles they have.
- Interior Angles of a Triangle — The sum of the interior angles of a triangle is always 180 degrees. Example: In a triangle, if two angles are 60 degrees and 70 degrees, the third angle is 50 degrees.
- Exterior Angle of a Triangle — The exterior angle of a triangle is equal to the sum of the two opposite interior angles. Example: If one exterior angle is 120 degrees, the two opposite interior angles could be 50 degrees and 70 degrees.
- Interior Angles of a Quadrilateral — The sum of the interior angles of a quadrilateral is 360 degrees. Example: In a rectangle, each angle is 90 degrees, adding up to 360 degrees.
- Interior Angles of a Regular Polygon — The sum of the interior angles of a regular polygon can be calculated by dividing the polygon into triangles. Example: A hexagon can be divided into 4 triangles, so the sum of its interior angles is 720 degrees.
- Exterior Angles of a Regular Polygon — The sum of the exterior angles of any regular polygon is always 360 degrees. Example: In a hexagon, each exterior angle is 60 degrees.
Exam Tips
Key Definitions to Remember
- Interior Angles of a Triangle
- Exterior Angle of a Triangle
- Interior Angles of a Quadrilateral
- Interior Angles of a Regular Polygon
- Exterior Angles of a Regular Polygon
Common Confusions
- Confusing the sum of interior angles with exterior angles
- Forgetting that the sum of exterior angles is always 360 degrees
Typical Exam Questions
- What is the sum of the interior angles of a triangle? 180 degrees
- How do you calculate the exterior angle of a triangle? It is equal to the sum of the two opposite interior angles
- What is the sum of the interior angles of a hexagon? 720 degrees
What Examiners Usually Test
- Understanding of how to calculate interior and exterior angles
- Ability to apply angle sum rules to solve problems