Angles and polygons.
Measure and reason about angles, then use those relationships to describe and classify polygons. Each rule is connected to a diagram and an explanation.
Work through the topic
Learn the method, follow the examples, then try the worksheet.
- 01
Measuring/classifying angles
Read an angle as a turn, measure from the correct zero and use its size to classify it.
- 02
Angles on lines and around points
Use straight-line and full-turn totals to find missing angles and explain each calculation.
- 03
Vertically opposite angles
Explain why opposite angles at intersecting straight lines are equal, then use the relationship to solve problems.
- 04
Parallel lines and transversals
Use the marked parallel lines to identify equal or supplementary angle pairs, and justify whether a rule applies.
- 05
Triangle angle sums
Use the triangle angle sum, equal sides and exterior angles to find missing angles with reasons.
- 06
Polygon angle sums
Build polygon angle totals from triangles, then distinguish regular polygons from irregular ones.
- 07
Classifying triangles/quadrilaterals
Classify triangles and quadrilaterals using sides, angles and parallelism, including shapes that belong to more than one family.
- 08
Shape-sorting rules and simple algorithms
Turn shape definitions into ordered decisions, test the rules and repair a classification algorithm.
Topic review
Revisit the key ideas, then choose a practice paper.