Let f:[a,b]->R be bounded. Further, let it be continuous on [a,b] except at points a1, a2, ...,an,... such that a1>a2>a3>...>an>...> a where an converges to a. Prove that f is Riemann integrable on [a,b]. It suffices to prove that f is integrable on [a,a1) (I've worked out that part). And that's what I'm having trouble with.