Find the points at which is continuous and at which is continuous.

Since

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

Similarly,

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