# Supplementary angles

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Supplementary angles are two angles with a sum of 180°. A common case is when they lie on the same side of a straight line.

### 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

- 1. Digital : Computer, geogebra application, projector.
- 2. Non digital : Worksheet and pencil.
- 3. Geogebra files : Supplementary angles.ggb

Download this geogebra file from this link.

### Process (How to do the activity)

- Prior hands on activity (optional – children can use news paper strips to make angles and place them together and notice if the resulting angle formed is a straight angle)
**.** - Students should be able to identify the types of angles in the file
- Let them attempt to join the two angle - They may try by coinciding different points or lines.
- Ask about the angle formed by joining the two angles
- Is the straight angle formed parallel to the x-axis.
- Challenge them to find another way to make a straight angle using the two existing angles.
- Interchanging the position of the two angles – ask what they notice.
- If one of the angle is changed will the two together again form supplementary angle.
- Readjust to make adjacent angles again to notice the resultant angle.
- Children can be asked to make note of the angle measures for different positions of the slider in the work sheet
- Ask students if the angles have to be adjacent to be supplementary pairs.
- Record the values of the two angles and their sum in the worksheet

Sl No. Value of slider α Angle ABC Angle DEF Sum Angle ABC + Angle DEF

Is angle ABC supplement of angle DEF

**Evaluation at the end of the activity**

- What are supplementary pair of angles?
- Is it required for the pair of angles to be adjacent to be supplementary?
- What type of angles form supplementary pair?