The base of an equilateral triangle is on the *x*-axis. What is the sum of the slopes of the three sides of the triangle?

Set up the triangle like this:

We know

*m*_{1}= 0. Let*m*_{2}=*b*/*a*, and*m*_{3}= –*b*/*a*. (We don’t need to know what*a*and*b*are.)So

*m*_{1}+*m*_{2}+*m*_{3}= 0.