May be this helps.
We have
Inserting
we get
Making substitution
we get
Show for that .
You may assume the error formula for the right rectangle rule: if exists and is continuous on , then for each there exists such that , which is greater than supposedly by error bound .
Attemp:
Let , then can be approximated by .
But I don't understand how to obtain the big O bound of using the right rectangle rule. I cannot see how the rule is relevant. Can someone please help?