E1: Start with the default setting: x1 = 0; n = 10.

Draw the magenta end point and observe the deviation of the rectangle sum (green point) from the analytic solution.

E2: Understand why the deviation is negative for x < π/2, and why it becomes zero at x = π . Reflect how summing mistakes can compensate for periodic functions.

E3: Increase the number of intervals with the slider and observe how the deviation changes and disappears in the limit.

E4: Change the initial point and consider why and how this shifts the analytic solution.

E5: Choose a large integration interval and consider why the rectangles lie below or above certain parts of the function.