1. Perpendicular lines Investigate the relationship between the gradients of perpendicular lines. What process would you suggest? Set up a table of values Gradient of Line123 Gradient of Perpendicular line

7. Perpendicular lines What patterns do you notice in the relationship between the gradients of perpendicular lines? What do you predict the gradient of the line perpendicular to a line with gradient 4 will be? What about a line perpendicular to a line with gradient ¾? Gradient of Line123 Gradient of Perpendicular line

8. Summarise what you have found For Perpendicular lines: If 2 line are perpendicular then the product of their gradient will equal -1.

9. Using what you have found Find the equation of the line perpendicular to y = 2x – 1, passing thru the point (1,1) Perpendicular gradient = -½  y = - ½ x + c substitute (1,1) 1 = - ½(1) + c  c = 1 ½ Therefore the perpendicular line is: y = - ½ x + 1

10. You to try Find the equation of the lines (i) parallel to and (ii) perpendicular to y = 3x + 4 passing thru (-1,2) Find the equation of the lines (i) parallel to and (ii) perpendicular to 2y – 3x = 5 passing thru (-1,2)