Parallel and Perpendicular

Parallel and perpendicular

• Parallel lines have the same gradient
• These three lines all have a gradient of 2
• Perpendicular means at right angles
• If a line has gradient m then any line perpendicular to it will have the gradient -1/m

Working it out

• Draw a sketch to find the gradient of line L
• The line slopes down/up so the gradient is negative/positive
• Use -1/m to calculate the gradient of P
• If m is a fraction you can just find its reciprocal and change the sign
• You might know P passes through() so you could use m=x and c=y to write the equation of line P
• Check it
  • If two lines are perpendicular the product of their gradient is the equation

Mid-points

• A line segment is a short section of a straight line
• You can find the mid-point of a line segment if you know the coordinates of the ends
• Coordinates of mid-point = average of x-coordinates, average of y-coordinates