The well known analytical formula for $SU(2)$ matrices $U = \exp(i \vec \tau \!\cdot\! \varphi\,) \cos|\vec \varphi\,| + i\vec \hat\varphi \, \sin|\vec \varphi\,|$\\ is extended to the $SU(3)$ group with eight real parameters. resulting involves sum over three roots of a cubic equation, corresponding so-called irreducible case, where one has employ trisection an angle. When going special unitar...