# Intersection of two lines

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### Objectives

To verify vertically opposite angles are equal

### Estimated Time

20 minutes

### Prerequisites/Instructions, prior preparations, if any

Knowledge about point, line, angle

### Materials/ Resources needed

Digital: Click here to open the file

Non-digital: Paper, pencil, ruler, compass, protractor

### Process (How to do the activity)

Download this geogebra file from this link.

**Procedure :**

- What are intersecting lines?
- Identify two lines cross each other in a plane i.e. lines 'g' and 'f' intersect at point 'A'
- Identify intersecting lines (two or more) meet only at one point always and also can cross each other at common vertex (which is the point of intersection).
- Identify the angles formed at common vertex 'A'
- Identify two pairs of opposite angles
- What is the vertically opposite angle?how many pair of vertically opposite angles are formed?
- Identify and measure vertically opposite angles?What is your conclusion?
- Can vertically opposite angles be adjacent?
- How many pairs of adjacent angles are formed?
- Idenify and measure adjacent angles?What is your conclusion?

### Evaluation at the end of the activity

- Can two lines cross at two points?
- If out of two angles of linear pair one is 60°, then what is the measure of other angle?
- If two angles are vertically opposite angles, where the measure of one of the angles is 30°, then what is the measure of other angle?

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