# How do I find the slope of a line through two points in three dimensions?

Since we are talking about a line in 3-D, it is more appropriate to talk about its direction vector than its slope. To find the direction vector $\vec{v}$ of the line passing through two points $\left({x}_{1} , {y}_{1} {z}_{1}\right)$ and $\left({x}_{2} , {y}_{2} , {z}_{2}\right)$ can be found by
$\vec{v} = \left({x}_{2} - {x}_{1} , {y}_{2} - {y}_{1} , {z}_{2} - {z}_{1}\right)$.