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Types of angles

CONCEPTUAL
Mathematics›Geometry|Ages 8—9|ID: mt_h0CVtqI2xo

Identify acute and obtuse angles; compare and order angles up to two right angles by size

Mastery Evidence

  • Classify given angles as acute, right, or obtuse
  • Order four angles from smallest to largest by visual comparison
  • Identify all acute and obtuse angles in a given triangle or quadrilateral

Assessment Prompt

“If [child] looks at the hands on a clock showing different times, can they tell you which angle between the hands is acute (sharper than a right angle) and which is obtuse (wider)?”

Prerequisites1

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  • Right Angles & Turns hard

    Identifying right angles and greater/less than right angle is prerequisite to naming acute/obtuse

    • Understanding angles hard

      Identifying right angles requires understanding what an angle is

      • 2-D shapes (age 6+) soft

        Understanding angles as shape properties requires knowing basic shape properties

        • Angles in triangles (age 6+) soft

          Understanding defining attributes supports describing shape properties formally

          • 2-D shapes hard

            Distinguishing defining vs non-defining attributes requires knowing common 2-D shape names first

          • 3-D shapes (age 5+) hard

            Identifying defining attributes builds on informal analysis and comparison of shapes

            • 2-D shapes hard

              Analysing and comparing shapes requires being able to name them first

            • 3-D shapes hard

              Analysing 3-D shapes requires recognising and naming them

        • 2-D shapes hard

          Describing properties of 2-D shapes (sides, symmetry) requires knowing the shapes first

        • 3-D shapes (age 5+) hard

          Formal property description extends informal analysis of sides and vertices

          • 2-D shapes hard

            Analysing and comparing shapes requires being able to name them first

          • 3-D shapes hard

            Analysing 3-D shapes requires recognising and naming them

      • Position, direction, and movement hard

        Recognising angles as turns extends Y2 work on quarter/half/three-quarter turns

        • Positional Language hard

          Position/direction vocabulary with right angles extends basic positional language

        • Turns & Directions hard

          Right-angle turns (clockwise/anti-clockwise) build directly on whole/half/quarter turns from Year 1

          • What Is a Half? soft

            Understanding half and quarter turns benefits from the concept of halves and quarters

            • Division as equal sharing hard

              Finding a half requires equal sharing into 2 groups — a division concept

              • Subtraction as taking away or separating hard

                Division as equal sharing/grouping requires understanding subtraction as taking away/separating

                • How Many in Total? hard

                  Understanding subtraction as taking away requires knowing numbers represent quantities (cardinality)

                  • One-to-one counting hard

                    Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'

          • Positional Language hard

            Describing movement and turns builds on positional language

    • Types of angles (age 8+) soft

      Identifying right angles and turns is supported by the convention of marking right angles with a small square

    • Position, direction, and movement hard

      Right angles as quarter turns extends Y2 turn vocabulary

      • Positional Language hard

        Position/direction vocabulary with right angles extends basic positional language

      • Turns & Directions hard

        Right-angle turns (clockwise/anti-clockwise) build directly on whole/half/quarter turns from Year 1

        • What Is a Half? soft

          Understanding half and quarter turns benefits from the concept of halves and quarters

          • Division as equal sharing hard

            Finding a half requires equal sharing into 2 groups — a division concept

            • Subtraction as taking away or separating hard

              Division as equal sharing/grouping requires understanding subtraction as taking away/separating

              • How Many in Total? hard

                Understanding subtraction as taking away requires knowing numbers represent quantities (cardinality)

                • One-to-one counting hard

                  Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'

        • Positional Language hard

          Describing movement and turns builds on positional language

Unlocks3