Now what I wanna do in this video is connect the first fundamental theorem of calculus to the second part, or the second fundamental theorem of calculus, which we tend to use to actually evaluate definite integrals. So let's think about, let's think about what f of, f of b, what f of b minus f of a is, what this is, where both b and a are also in this interval. So f of b, and we're gonna assume that b is larger than a. So let's say that b is this right over here. Let me do that in the same color. So let's say that b is right over here. F of b is going to be equal to, we just literally replaced the b where you see the x, it's going to be equal to the definite integral between c and b of f of t, dt, which is just another way of saying, it's just another way of saying is the area under the curve between c and b.