## tc1979 4 years ago How can you determine if two lines are perpendicular?

1. chaise

There gradients will multiply to give negative one (-1). :)

2. chaise

Their*?

3. bnut056

if lines are perpendicular their dot product will be 0 zero

4. tc1979

can you elaborate?

5. chaise

For example. If you have a line given by y = 10x+3 and also y=-1/10x+5 Where the gradient is marked by the number before the x. The two numbers multiply to give negative one. Make sense?

6. 5369855

Their ratio will be the same. Ex: 10x + 5 and 20x+10. to get from 10x+5 to 20x+10, you multiply the first one by 2

7. Stroodle

If the product of the two gradients is -1 they are perpendicular.

8. 5369855

*you must solve for the dot product. if you want it to be parallel, ratio must be the same

9. polpak

You all need to remember your algebra 2. At this stage it's just a matter of comparing slopes. If the two slopes are perpendicular they will multiply to make -1. Or you can find one given the other by the fact that they will be negative reciprocals of each other. If you are given a slope of 10 as in the example above, a perpendicular slope will be -1/10. And for any slope r, a perpendicular slope will be -1/r.