How do you find the slope of a line perpendicular to a slope of a line is 1/3?
In general, if the slope of a line is
To see that, consider a line given by
If you reflect that line in the line
If you then reflect that line in the
The total result of these two geometric operations is to rotate the original line through a right angle (try it yourself with a square of paper).
Now we can rearrange this new line's equation into slope intercept form as follows:
Divide both sides by
Notice the new slope is