For the other integral, since |sin x/x| < 1 for x > 0, we get
R
0
e−x R sin x
x
dx
≤
R
0
e−x R dx = 1 − e−R2
R ,
which also converges to 0 as R → ∞.
We note that these estimates are identical to those used in [2] to show that the
order of integration makes no difference in the double integral. Thus, we can view this
Green’s Theorem calculation as a modification of the double integral method.