Question

Just a question or questions about some concept in general. (Riemann Sum, Midpoint Sum, Sums using Trapezoids...)

Answer 1

Lets say I am asked to find the area under the curve, and I am doing left-ends sum. (Estimation using rectangles)

So, I am asked to fill in the table, and there I start,

x y
--------
x1 y1
x2 y2
x3 y3
x4 y4
x5 y5



So the values I put for the y, are the values that of f(x1), f(x2), f(x3) and on... OR
am I putting the y values where the rectangles are going to meet, saying the y-values that correspond to the height of the rectangle but not (necessarily correspond) to the function?