  In this short paper, I introduce an elementary method for exactly evaluating
the definite integrals $\, \int_0^{\pi}{\ln{(\sin{\theta})}\,d\theta}$,
$\int_0^{\pi/2}{\ln{(\sin{\theta})}\,d\theta}$,
$\int_0^{\pi/2}{\ln{(\cos{\theta})}\,d\theta}$, and
$\int_0^{\pi/2}{\ln{(\tan{\theta})}\,d\theta} \,$ in finite terms. The method
consists in to manipulate the sums obtained from the logarithm of certain
products of trigonometric functions at rational multiples of $\pi$, putting
them in the form of Riemann sums. As this method does not involve any search
for primitives, it represents a good alternative to more involved integration
techniques. As a bonus, I show how to apply the method for easily evaluating
$\,\int_0^1{\ln{\Gamma(x)} \, d x}$.
