Examples 7.1.6(c):
Find conditions for a function so that the upper sum can be
computed by always taking the left endpoint of each subinterval
of the partition, or conditions for always being able to take
the right endpoints.
To ensure, for example, that the left endpoint will always be used
for the computation of a lower sum we must ensure that regardless
of the partition that was chosen the function takes its smallest
value inside every partition subinterval on its left endpoint.
We will leave it to you to find the correct condition(s), but you can use the applet below to experiment with various functions.

Click on Options and use the functions:
