# Perpendicular lines

- Author:
- swharton

- Topic:
- Straight Lines

**Perpendicular lines**Use the sliders and the instructions below to explore what happens to the angle between these two lines.

What can you find out about perpendicular lines
1 Make m1 = 2 and m2 = - 1/2. What do you notice about the lines?
2 Write the equations for both lines.
3 Now change the value of c for one of the lines.What happens to the angle between the lines.
Write the equations for these new lines.
4 Look at these four equations for straight lines. Can you

**predict**which 2 will be parallel? y = 4x + 2, y = -4x + 2, y = -1/4x + 5, y = 4x + 1/2 5 Use the worksheet to check your prediction. 6 There is a relationship between the equations for perpendicular lines. Can you spot it? This web link might help you www.mathsisfun.com/reciprocal.html