Mathematics·Geometry·procedural
Angle sums in triangles and polygons
Derive and use the angle sum in a triangle (180°), use it to deduce the angle sum in any polygon ((n−2) × 180°), and calculate interior and exterior angles of regular polygons
Suggested ages 11–14
Evidence of understanding
- Calculate a missing angle in a triangle by subtracting the known angles from 180°
- Find the sum of interior angles in a hexagon by dividing it into triangles
- Calculate each interior and exterior angle of a regular polygon given the number of sides
Assessment prompt
If Angle sums in triangles and polygons knows two angles of a triangle are 50° and 70°, can they work out the third? And can they figure out the angles inside a regular pentagon?
Standards alignment
8.G.5US · ccss-math
Angle arguments and similarity
Common Core State Standards for Mathematics · 8
KS3.Maths.Geo.12GB · uk-nc-2013
Sum of Angles in Polygons
The national curriculum in England: Key stages 1 and 2 framework document · Key Stage 3