\[1)\ 84{^\circ}:\]
\[a = \frac{1}{2} \bullet 84{^\circ} = 42{^\circ}.\]
\[2)\ 110{^\circ}:\]
\[a = \frac{1}{2} \bullet 110{^\circ} = 55{^\circ}.\]
\[3)\ 230{^\circ}:\]
\[a = \frac{1}{2} \bullet 230{^\circ} = 115{^\circ}.\]
\[4)\ 340{^\circ}:\]
\[a = \frac{1}{2} \bullet 340{^\circ} = 170{^\circ}.\]