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!