Perpendicular lines and slopes
The slopes of two perpendicular lines are the negative reciprocals of each other.
This means if m1 is the slope of line 1 and m2 is the slope of line 2, then:
m1 * m2 = -1
We are given the slope m1=-3. To find the slope that is perpendicular to m1, we solve the equation for m2 as follows:
Substituting m1=-3:
The required slope is 1/3