\(\begin{array}{l}
\angle ABC = {50^0} \Rightarrow \angle ACB = {90^0} - \angle ABC = {90^0} - {50^0} = {40^0}.\\
AC = AB.\tan \angle ABC = 3.\tan {50^0} \approx 3,58\,\,cm.\\
BC = \sqrt {A{B^2} + A{C^2}} = \sqrt {{3^2} + 3,{{58}^2}} \approx 4,67\,\,cm.
\end{array}\)