Edexcel IGCSE Maths 复习笔记 3.7.1 Perpendicular Lines

Edexcel IGCSE Maths 复习笔记 3.7.1 Perpendicular Lines

What are perpendicular lines?

  • You should already know that PARALLEL lines have equal gradients
  • PERPENDICULAR LINES do meet each other and where they do the two lines form a right angle – ie they meet at 90°

What’s the deal with perpendicular gradients (and lines)?

  • Before you start trying to work with perpendicular gradients and lines, make sure you understand how to find the equation of a straight line – that will help you do the sorts of questions you will meet
  • Gradients m1 and m2 are PERPENDICULAR if m1 × m2 = -1
  • We can use m2 = -1 ÷ m1 to find a perpendicular gradient 

    (This is called the NEGATIVE RECIPROCAL)If in doubt, SKETCH IT!

Worked Example