FunctionsCourse skill

Equations of perpendicular lines

Use negative reciprocal gradients for two non-vertical perpendicular lines.

  • For non-zero gradients, , so .
  • Use the new gradient with the given point.
  • A horizontal line is perpendicular to a vertical line.

Example 1

Take the negative reciprocal

Find the equation of the line. Through , perpendicular to .

Apply this to both sides.

Example 2

Determine the equation of the required line. Through , perpendicular to .

Apply this to both sides.

Your turn

Question 1

Find the equation of the line through perpendicular to .

Check answer
Apply this to both sides.
Question 2

Find the equation of the line through perpendicular to .

Check answer
Apply this to both sides.
Question 3

Find the equation of the line through perpendicular to .

Check answer
Apply this to both sides.
Question 4

Find the equation of the line through perpendicular to .

Check answer
Apply this to both sides.
Question 5

Find the equation of the line through perpendicular to .

Check answer
Apply this to both sides.
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