Angle Properties

Scheme of work: GCSE Foundation: Year 9: Term 6: Angle Properties

Prerequisite Knowledge

  • Know angles are measured in degrees: estimate and compare acute, obtuse and reflex angles.
  • Draw given angles, and measure them in degrees (°)
  • identify:
    • angles at a point and one whole turn (total 360°)
    • angles at a point on a straight line and 1/2 a turn (total 180°)
    • other multiples of 90°

Success Criteria

  • use conventional terms and notations: points, lines, vertices, edges, planes, parallel lines, perpendicular lines, right angles, polygons, regular polygons and polygons with reflection and/or rotation symmetries;
  • use the standard conventions for labelling and referring to the sides and angles of triangles; draw diagrams from written description
  • apply the properties of angles at a point, angles at a point on a straight line, vertically opposite angles;
  • understand and use alternate and corresponding angles on parallel lines;
  • derive and use the sum of angles in a triangle (e.g. to deduce use the angle sum in any polygon, and to derive properties of regular polygons)

Key Concepts

  • Understanding the basic angle properties, such as the types of angles helps students with angle measurements.
  • Rather than being told (or given) angle properties students should have the opportunity to discover and make sense of them practically.
  • Use the Geogebra files to demonstrate the angle properties.
  • Geometric problems can often be solved using various angle properties. Encourage students to look for alternative properties.
  • Demonstrate how a polygon is made up from interior triangles when calculating their angles.

Common Misconceptions

  • When measuring angles using a 180-degree protractor, students often confuse the upper and lower scale. Understanding basic angle properties such as acute and reflex angles helps with this.
  • Students often forget the definition of properties associated to angles in parallel lines.
  • Exterior angles in a polygon have to travel in the same direction for the sum to be 360°.

Angle Properties Resources

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