# Vertically opposite angles

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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 Vertically opposite 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”

Download this geogebra file from this link.

### Process (How to do the activity)

- 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).
- Students to identify number of angles formed when the two lines cross each other
- Name the all the angles formed around the point
- Do the angles formed have a relation
- Identify angles on AB: what do the form together
- Identify angles on CD: what do they form together
- What is observed about these angle pairs on the two lines
- Can you find other pair of angles on line AB and CD
- What is common about these angles
- Record the values of the angles formed and their sum in the worksheet

Sl No.

Value ofslider α

Angles on line AB ∠DOA+ ∠BOD Angles on line CD ∠ DOA+∠AOC Common angle the lines share ∠ DOA ∠ BOD ∠ DOA ∠ AOC .

**Evaluation at the end of the activity**

- What is the angle measure of the sum of any two adjacent angles when two lines intersect?
- What is the total measure of all the angles formed when two lines intersect?