# Parallel lines and Perpendicular lines

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### Objectives

To enable students to-

- understand the concept of parallel lines and perpendicular lines;
- identify differences between parallel lines and non parallel lines;
- understand about when two lines can be parallel (constant perpendicular distance)
- to measure the perpendicular distance between two lines.
- to provide hands-on experience through Geogebra application.

### Estimated Time

90 minutes

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

Prior understanding of lines and angles, right angle as 90 degree, use of protractor to measure/draw an angle.

### Materials/ Resources needed

- Digital : Computer, Geogebra application, projector.
- Non-digital : Geometrical tools, pencil and worksheet.

### Process (How to do the activity)

**Teachers work:**

- Show examples of pictures with parallel and non-parallel lines.
- Help students to identify their differences.
- Ask students on how they can conclude two line/segments are parallel and record the same.
- Introduce about the concept of perpendicular lines
- Help students understand that perpendicular line is the shortest distance between a pair of lines.
- Demonstrate using Geogebra how to plot parallel lines and check if perpendicular distance remains fixed between them.
- Ask students to give more examples of parallel lines in real life situations and their importance.

**Students work:**

- Identify the difference between parallel and non-parallel lines.
- Identify the parallel lines in their surroundings and measure the distance between them at various regions.
- Plot parallel lines using Geogebra and try to measure perpendicular distance between them.
- Plot perpendicular line using Geogebra and understand it as the shortest distance between two lines.
- Analyse the importance of parallel lines in real life situations.

### Developmental questions of the activity

- When can we say two lines to be parallel and non-parallel?
- What is the shortest distance between a pair of parallel lines?
- What is the angle measurement of line drawn as shortest distance between the pair of parallel lines?
- What is the length of the perpendicular line drawn at various positions between two parallel lines?
- Where do you see perpendicular lines in our surroundings?
- Where do you see parallel lines in real life situations? What is the importance of lines been parallel in them?

#### Application questions:

- Why are the rods of a window parallel?
- Why are the electric cables laid parallel to each?
- Can buildings have slant or perpendicular pillars? Why?
- Why are Football stadiums rectangles?
- Why are doors and windows usually rectangular?
- Why are some crops grown in fields parallel(example-cabbage)?
- Why we should not cross road diagonally?