Unit G2.3

Perpendicular lines

Activity 1 Plot the lines y= 4x-1 and y = -¼ x-1
You should notice that these lines are perpendicular to each other. (At right angles)

Now plot the following lines. Clear the screen after each pair.

1. y = 3x + 2 and y = -1/3 x +1

2. y = -4x -1 and y = ¼ x +2

3. y= 2/3 x and y = -3/2 x +1

4. y = - 5/7 x -2 and y = 7/5 x -1

You should get lots of pairs of perpendicular lines.
Can you work out what the rule is for the gradients of perpendicular lines.

Activity 2

For each question, plot the line given and a line perpendicular to it. (It doesn't matter about the intercept)

1. y = 2x + 2

2. y = ½ x -3

3. y = -5x

4. y = - 1/7 x + 1

5. y = ¾ x -1

Activity 3*

For each question plot the line given and the line perpendicular going through the point given.

1. y = 3x (0,2)

2. y = -1/4 x (0,1)

3. y = 2x (1,2)

4. y = -2/3 x (-1,3)