To find the last measurement in the trapezoidal rule, which variable is used?

In the context of the trapezoidal rule, the last measurement is associated with the variable that represents the difference in the values of the dependent variable (the function you are integrating) over the last interval. This is typically denoted as (dl) as it corresponds to the change in the variable in the last segment of the interval being considered.

The trapezoidal rule approximates the area under a curve by dividing it into multiple trapezoids, using the heights (function values) at each end of these intervals. The last measurement contributes to defining the last trapezoid's dimensions, thereby influencing the total area under the curve that the trapezoidal rule estimates.

In contrast, (h) often represents the width of the subintervals, while (Df) could be interpreted in various contexts but doesn't specifically indicate the last measurement in the trapezoidal rule. (A) is frequently related to area but does not denote a specific measurement within the context of the trapezoidal rule's application.

Thus, using (dl) clearly identifies the last segment's value, making it the appropriate choice for determining the last measurement in the trapezoidal rule.