So let's say we're looking at a point right over there. The slope of the tangent line, it tells us for a very small change in t, I'm exaggerating it visually, for a very, very small change in t, how much are we changing in position? How much are we changing in position? So we write that as ds dt is the derivative of our position function at any given time. So when we're talking about how the rate at which position changes with respect to time, what is that? Well, that is equal to velocity. So this is equal to velocity.