Log Cosine Function
By analogy with the log sine function, define the log cosine function by
![C_n=int_0^(pi/2)[ln(cosx)]^ndx.](http://mathworld.wolfram.com/images/equations/LogCosineFunction/NumberedEquation1.gif) |
(1)
|
The first few cases are given by
where
is the Riemann zeta function.
The log cosine function is related to the log sine function by
 |
(5)
|
and the two are equal if the range of integration for
is restricted from 0 to
to 0 to
.
Oloa (2011) computed an exact value of the log cosine integral
 |
(6)
|
where
is the Riemann zeta function,
is the Euler-Mascheroni constant,
is a multivariate zeta function, and
denotes
. A closed form for
in terms of more elementary functions is not known as of Apr. 2011, but it is numerically given by
 |
(7)
|
(Oloa 2011; OEIS A189272).
REFERENCES:
Oloa, O. "A Log-Cosine Integral Involving a Derivative of a MZV." Preprint. Apr. 18, 2011.
Sloane, N. J. A. Sequence A189272 in "The On-Line Encyclopedia of Integer Sequences."