Perpendicular lines are lines which cross at a right angle.
If the gradient of a line is m, then the gradient of a perpendicular line is .
When we multiply the gradients of two perpendicular lines, we get an answer of -1.
Find the gradient of a line which is perpendicular to a line with gradient:
a) 3 × -1/3 = -1, so the gradient is =1/3
b) -1/4 × 4 = -1, so the gradient is 4
c) 1.5 × -2/3 = -1, so the gradient is -2/3
Find the gradient of a line which is perpendicular to 2y = 6x - 1.
You need to rearrange the equation into the form y = mx + c. m will be the gradient
2y = 6x - 1
y = 3x - 1/2
The gradient of this line is 3.
The gradient of the perpendicular line is -1/3, because 3 × -1/3 = -1.