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Properties of 2D shapes introduces students to key vocabulary used to describe the uniqe properties of 2D and 3D shapes. This is a prerequisite unit before moving on to drawing 3D shapes in Term 2 of Year 9. Learning progresses from describing 2D shapes to performing basic transformations such as rotations, enlargements, translations and reflections.

**Prerequisite Knowledge**

- distinguish between regular and irregular polygons based on reasoning about equal sides and angles.
- know angles are measured in degrees: estimate and compare acute, obtuse and reflex angles
- draw 2-D shapes using given dimensions and angles

**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
- derive and apply the properties and definitions of: special types of quadrilaterals, including square, rectangle, parallelogram, trapezium, kite and rhombus; and triangles and other plane figures using appropriate language
- identify and apply circle definitions and properties, including: centre, radius, chord, diameter, circumference, tangent, arc, sector and segment

**Key Concepts**

- Understanding and using the vocabulary is key throughout this topic.
- Regular polygons are closed shapes with straight lines of equal length.
- Students need to recognise different types of quadrilaterals and triangles by their geometrical properties.
- All shapes have a rotational symmetry of at least one.
- Reflected vertices are an equal distance from the line of symmetry.

**Common Misconceptions**

- Students often confuse the part of a circle.
- Diagonal lines do not have to be slanted and can be horizontal or vertical.
- A circle is not a polygon since its edge of not straight.
- Rectangles are incorrectly assumed to have a rotational symmetry of order 4.

May 1, 2019

In this blog I will share some practical tips for using mini-whiteboards in a mathematics lesson. I use mini-whiteboards nearly every lesson because they help the students show me the progress they are making. When I understand what the misconceptions are I am able to address them in subsequent examples as part of my feedback. […]

April 17, 2019

Demonstrating student progression during a mathematics lesson is about understanding the learning objective and breaking that down into explicit success criteria. Using Success Criteria Take, for example, a lesson on calculating the area of compound rectilinear shapes. The intended learning objective was written on the main whiteboard. Success criteria were used to break down the individual […]

March 26, 2019

Plotting and interpreting conversion graphs requires linking together several mathematical techniques. Recent U.K. examiner reports indicate there are several common misconceptions when plotting and interpreting conversion graphs. These include: drawing non-linear scales on the x or y axis, using the incorrect units when converting between imperial and metric measurements, taking inaccurate readings from either axis not […]