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 ÷ m2 to find a perpendicular gradient
(This is called the NEGATIVE RECIPROCAL)
If in doubt, SKETCH IT!