To find an antiderivative of
f(
z), we go through
our list of integration methods:
- Recognize elementary antiderivatives
- Rewrite the integrand to make it easier
- Use substitution to reverse the chain rule or simplify the
integrand
- Use integration by parts
- Use inspection to see the value of a definite
integral
to find one that works for this integrand. In this case,
only one method is appropriate. We use substitution to rewrite the integrand in terms of
w = ln(
z).
This is shown below.
Substitution:
Let
w = ln(
z). Then
w' = 1/
z, so
dw = (1/
z)
dz.
The integral can therefore be rewritten as

( ln(
z)
5 )/
z dz =
w5 dw =
(1/6)
w6 +
C
Thus, substituting back for
w,

( ln(
z)
5 )/
z dz =
(1/6) ln(
z)
6 +
C
To evaluate the definite integral, we take this antiderivative,
evaluate it at the endpoints of the integral (1/e and 1),
and take the difference of the values. This gives
[ (1/6) ln((1))6 ] - [ (1/6) ln((1/e))6 ] = -1/6.