The cyclic group \(\{\mathbf{E}, \mathbf{A}, \mathbf{B}\}\) for the rotation of an equilateral triangle by \(0^{\circ}, 120^{\circ}\), and \(240^{\circ}\) has a matrix representation

\[
\begin{array}{ccc}
\left(\begin{array}{ll}
1 & 0 \\
0 & 1 \end{array}ight) & \left(\begin{array}{cc}
-\frac{1}{2} & \frac{\sqrt{3}}{2} \\
-\frac{\sqrt{3}}{2} & -\frac{1}{2}
\end{array}ight) & \left(\begin{array}{cc}
-\frac{1}{2} & -\frac{\sqrt{3}}{2} \\
\frac{\sqrt{3}}{2} & -\frac{1}{2}
\end{array}ight) . \\
D(\mathbf{E}) & D(\mathbf{A}) & D(\mathbf{B})
\end{array}
\]
Show that this representation is reducible.