Find the points at which is continuous and at which is continuous.
and , are continuous everywhere we know (by Theorem 3.2) that is continuous everywhere is not zero. We proved in this exercise (Section 2.8, #1 (b) of Apostol) that
Thus, is continuous for
and by Theorem 3.2 we then have is continuous everywhere that is not zero. We proved in the same exercise (Section 2.8, #1(a) of Apostol) that
Hence, is continuous for