Step 5 Objective

Identify parallel and perpendicular lines; know the sum of angles at a point, on a straight line and in a triangle and recognise vertically opposite angles.

Examples of what pupils should know and be able to do

Probing questions

How do you go about identifying parallel lines?

Give me some examples of shapes that have pairs of parallel lines.

What do you understand by perpendicular lines? Can a triangle have sides that are a pair of perpendicular lines? Why?

Is it possible to draw a triangle with:

Give an example of each triangle, suggesting th esizes of the three angles, if it is possible. If it is impossible, explain why.

What if pupils find this a barrier?

Show a diagram of a set of parallel lines with one or more transversals and use tracing paper to copy one of the angles. Find all the angles on the diagram that are equal to that angle.

Which angles involve turning the tracing paper and which angles don't?

Investigate cutting out different triangles, tearing off the corners and demonstratin that the three corners fit on a straight line regardless of the size or shape of the triangle. Perform a similar activity with quadrilaterals.

diagram demonstrating that the three corners fit on a straight line

Investigate cutting out different triangles, tearing off the corners to demonstrate that the four angles meet at a point, with sum 360°

two equal angles

The two marked angles are equal. Cut them out, or trace them, and superimpose one on the other, to check this.