And we can see just visually, it looks like right over here the slope of the tangent line looks like the same as the slope of the secant line. It also looks like the case right over here, the slope of the tangent line is equal to the slope of the secant line. And it makes intuitive sense. At some point, your instantaneous slope is going to be the same as the average slope. Now how would we write that mathematically? Well let's calculate, let's calculate, well let's calculate the average slope over this interval. Well the average slope over this interval, or the average change, the slope of the secant line, is going to be our change in y, our change in y right over here, over our change in x, over our change in x.