\[\boxed{\mathbf{426.}}\]
\[1)\ a = 4,5\pi:\]
\[a = 0,5\pi + 4\pi = \frac{\pi}{2} + 2 \bullet 2\pi\]
\[a_{0} = \frac{\pi}{2} = \left( \frac{180}{\pi} \bullet \frac{\pi}{2} \right)^{{^\circ}} = \left( \frac{180}{2} \right)^{{^\circ}} =\]
\[= 90{^\circ}\]
\[Точка\ P\ повернется\ на\ угол\ 90{^\circ}\ \]
\[против\ часовой\ стрелки:\]
\[2)\ a = 5,5\pi:\]
\[a = 1,5\pi + 4\pi = \frac{3\pi}{2} + 2 \bullet 2\pi\]
\[a_{0} = \frac{3\pi}{2} = \left( \frac{180}{\pi} \bullet \frac{3\pi}{2} \right)^{{^\circ}} =\]
\[= (90 \bullet 3)^{{^\circ}} = 270{^\circ}\]
\[a_{1} = 270{^\circ} - 360{^\circ} = - 90{^\circ}\]
\[Точка\ P\ повернется\ на\ угол\ 90{^\circ}\ \]
\[по\ часовой\ стрелке:\]
\[3)\ a = - 6\pi:\]
\[a = 0 - 6\pi = 0 - 3 \bullet 2\pi\]
\[a_{0} = 0\]
\[Точка\ P\ останется\ на\ прежнем\ \]
\[месте:\]
\[4)\ a = - 7\pi = \pi - 8\pi =\]
\[= \pi - 4 \bullet 2\pi\]
\[a = \pi = \left( \frac{180}{\pi} \bullet \pi \right)^{{^\circ}} = 180{^\circ}\ \]
\[Точка\ P\ повернется\ \]
\[на\ угол\ 180{^\circ}:\]