Alternate angles

I can recognise that a pair of parallel lines traversed by a straight line produces equal alternate angles.

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Year 8

Alternate angles

I can recognise that a pair of parallel lines traversed by a straight line produces equal alternate angles.

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Lesson details

Key learning points

Alternate angles can be identified in an arrangement of 3 line segments.
If two of the lines are parallel these alternate angles are equal.
Knowledge of alternate angles can be used to find unknown angles.
Knowledge of corresponding and alternate angles can be used to find unknown angles.

Common misconception

Referring to alternate angles as 'Z' angles because of the arrangement of the lines.

Modelling the justification correctly through every example and using exterior alternate angles to highlight the limitations of 'Z' angles.

Keywords

Alternate angles - A pair of angles both between or both outside two line segments that are on opposite sides of the transversal that cuts them.

If available, use mini-whiteboards and ask the students to draw a diagram that shows "exterior alternate angles", "interior alternate angles", "equal interior alternate angles" etc.

Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).