$ \displaystyle\lim_{x \to \frac{\pi}{3}} \frac{sin(3x+2\pi)}{3x-\pi} = $
$ = \displaystyle\lim_{x \to \frac{\pi}{3}} \frac{sin(3x)}{3x-\pi} = $
$ = \displaystyle\lim_{x \to \frac{\pi}{3}} \frac{-sin(3x-\pi)}{3x-\pi} = $
Con un cambio di variabile al volo $t = 3x-\pi$ si conclude
$ = \displaystyle\lim_{t \to 0} - \frac{sint}{t} = - 1 $