Actually, let me do it in that same... Well, I'm now using the purple for a different purpose than just the first trapezoid. Hopefully you realize that. I was just sticking with that pen color. Then f of 3, 3 minus 1 is 2, square root of 2. So the function evaluated at 3 is the square root of 2, so this is going to be 2 times the square root of 2. Then the function evaluated at 4. When you evaluate at 4, you get the square root of 3, so this is going to be 2 times the square root of 3.