Parallel lines

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Relation between angles that are formed in multiple parallel lines is investigated with geogebra sketch.


To understand corresponding angles are equal

To understand  alternate angles are equal

Estimated Time

30 minutes

Prerequisites/Instructions, prior preparations, if any

Prior knowledge of point, lines, angles, intersecting lines, vertically opposite angles

Materials/ Resources needed

  • Digital : Computer, geogebra application, projector.
  • Non digital : Worksheet and pencil.
  • Geogebra files : Parallellines-3.ggb

Download this geogebra file from this link.

Process (How to do the activity)

  • Use the file to seek the initial observations from children – number of lines, are the lines parallel, line that acts as a transversal.
  • Ask how many angles are there present. List all the angles formed.
  • Additional information can be retrieved – no of angles are formed at each point, number of angle pairs, number of linear pairs at each point.
  • Talk about supplementary angle pairs – let them identify the supplementary angle pairs for the parallel lines.
  • Move the transversal using point D to observe the changes made by the transversal with the parallel lines.
  • Children can observe the pair of angles that vary equally
  • Mention corresponding angles and their properties
  • For a give pair of parallel lines list all the corresponding angles.
  • Use point B to show that lines need not be parallel with x-axis to be parallel with each other.
  • Inquire about number of parallel lines that can be drawn for a given line.
  • Change the position of point D to record other values
Angle BPD Angle DPQ Total Angle KMP Angle PMN Total Angle ECM Angle MCL Total
  • Evaluation at the end of the activity