CBSE · Class 6-12

Class 8 · Ganita Prakash

Unit 11 · Class 8Ganita Prakash

Exploring Some Geometric Themes

Angles in polygons, tessellations, transformations.

Lessons

3 concepts

1
Polygon Angle Facts
Triangulate an $n$ -gon into $n-2$ triangles → sum is $(n-2)\cdot 180°$ . For regular, divide by $n$ .
2
Exterior Angles
As you walk once around any convex polygon, turning at each vertex, the total turn = $360°$ . So exterior angles sum to $360°$ regardless of number of sides.
3
Transformations
Translation slides. Rotation turns about a fixed centre. Reflection flips across a line. All three preserve size and shape.

Skills to practise

Skill · medium

Exploring Some Geometric Themes — Practice