Parallel & Perpendicular Gradients (Edexcel IAL Maths)

Spec point — 2.2

Parallel & perpendicular gradients

What are parallel lines?

• Parallel lines are equidistant meaning they never meet
• Parallel lines have equal gradients

What are perpendicular lines?

• Perpendicular lines meet at right angles
• The product of their gradients is -1

What does collinear mean?

• Collinear line segments are two line segments that are part of the same line

• They have equal gradients

  • They may pass through, or meet at, a common point
  • When they are extended, they become the same line

• Rearrange their equations into the same form and they will be identical

How do I tell if lines are parallel or perpendicular?

• Rearrange equations into the form y = mx + c
• m is the gradient

Exam Hint

• Exam questions are good at “hiding” parallel and perpendicular lines.
• For example a tangent and a radius are perpendicular.
• Parallel lines could be implied by phrases like “… at the same rate …”

Worked Example