ln x = t
x = e^t
dx = e^t dt
S cos t * e^t dt =
e questo lo fai per parti
= e^t sin t - S e^t sin t dt =
= e^t sin t - [ - e^t cos t - S - e^t cos t dt ]
2 S e^t cos t dt = e^t ( sin t + cos t ) + C
S cos (ln x) dx = 1/2 x ( sin ln x + cos ln x ) + C