Vertically opposite angles

When two straight lines intersect each other four angles are formed.The pair of angles which lie on the opposite sides of the point of intersection are vertically opposite angles.

Objectives
Introduce children to concept of supplementary angles

Estimated Time
30 minutes

Prerequisites/Instructions, prior preparations, if any
Prior knowledge of point, lines, angles

Materials/ Resources needed

 * Digital : Computer, geogebra application, projector.
 * Non digital : Worksheet and pencil.
 * Geogebra files : “Vertically opposite angles.ggb”

Process (How to do the activity)

 * 1) Prior hands on activity (optional – children can use 2 strips newspaper or sticks to form vertically opposite angles and note the changes in the angles with change in the position of the strips or sticks).
 * 2) Students to identify number of angles formed when the two lines cross each other
 * 3) Name the all the angles formed around the point
 * 4) Do the angles formed have a relation
 * 5) Identify angles on AB: what do the form together
 * 6) Identify angles on CD: what do they form together
 * 7) What is observed about these angle pairs on the two lines
 * 8) Can you find other pair of angles on line AB and CD
 * 9) What is common about these angles
 * 10) Record the values of the angles formed and their sum in the worksheet
 * {| class="wikitable"

Sl No. Value ofslider α
 * rowspan="2" |
 * rowspan="2" |
 * colspan="2" |Angles on line AB
 * rowspan="2" |∠DOA+ ∠BOD
 * colspan="2" |Angles on line CD
 * rowspan="2" |∠ DOA+∠AOC
 * rowspan="2" |Common angle the lines share
 * ∠ DOA
 * ∠ BOD
 * ∠ DOA
 * ∠ AOC
 * }
 * Evaluation at the end of the activity
 * 1) What is the angle measure of the sum of any two adjacent angles when two lines intersect?
 * 2) What is the total measure of all the angles formed when two lines intersect?
 * }
 * Evaluation at the end of the activity
 * 1) What is the angle measure of the sum of any two adjacent angles when two lines intersect?
 * 2) What is the total measure of all the angles formed when two lines intersect?
 * }
 * Evaluation at the end of the activity
 * 1) What is the angle measure of the sum of any two adjacent angles when two lines intersect?
 * 2) What is the total measure of all the angles formed when two lines intersect?
 * Evaluation at the end of the activity
 * 1) What is the angle measure of the sum of any two adjacent angles when two lines intersect?
 * 2) What is the total measure of all the angles formed when two lines intersect?