Question

How can you determine if two lines are perpendicular?

Answer 1

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

Answer 2

Their*?

Answer 3

if lines are perpendicular their dot product will be 0 zero

Answer 4

can you elaborate?

Answer 5

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?

Answer 6

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

Answer 7

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

Answer 8

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

Answer 9

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.