Angle Facts in a Figure
Unknown angles fall out of a small set of facts: a straight line is 180 degrees, a triangle sums to 180, a quadrilateral to 360, angles combine and split, and parallel lines give equal corresponding/alternate angles. Learners apply these from clock faces and single figures up to polygon angle sums via triangulation and auxiliary lines. The method is choosing the right fact and chaining equations.
grade 4 GeometryMeasurement & data Draw a DiagramConvert to Algebra
Progression (13)
g4 1. A clock face is twelve equal 30-degree parts Measurement & data
g4 2. Small angles combine into larger angles Measurement & data
g4 3. Use the 180-degree line to find figure angles Measurement & data
g4 4. Split a polygon into triangles to sum angles Measurement & data
g4 5. Quadrilateral angles sum to 360 degrees Measurement & data
g4 6. A straight line is 180 degrees Measurement & data
g4 7. Triangle angles sum to 180 degrees Measurement & data
g4 8. Draw an auxiliary parallel line to find a bent angle Geometry
g4 9. Corresponding and alternate angles are equal Geometry
g4 10. Adjacent angles of a parallelogram sum to 180 Geometry
g4 11. Perpendicular is half of a straight angle GeometryMeasurement & data
g4 12. Exterior angle sum of a regular polygon is 360 GeometryMeasurement & data
g4 13. Polygon angle sum via triangulation from a vertex Geometry