\[\boxed{\mathbf{783.еуроки - ответы\ на\ пятёрку}}\]
\[\mathbf{Памятка:как\ определить\ }\]
\[\mathbf{градусную\ меру\ угла\ }\]
\[\mathbf{по\ клеткам.}\]
\[\textbf{а)}\ \angle ABC = \frac{1}{2}\angle AOC = \frac{1}{2} \cdot 90{^\circ} =\]
\[= 45{^\circ}.\]
\[\textbf{б)}\ \angle ABC = \frac{1}{2}\angle AOC = \frac{1}{2} \cdot 90{^\circ} =\]
\[= 45{^\circ}.\]
\[\textbf{в)}\ \angle AOC = 90{^\circ} + 30{^\circ} = 120{^\circ};\]
\[\angle ABC = \frac{1}{2}\angle AOC = 60{^\circ}.\]
\[\textbf{г)}\ \alpha = 360{^\circ} - 90{^\circ} = 270{^\circ};\]
\[\angle ABC = \frac{1}{2}\alpha = \frac{1}{2} \cdot 270{^\circ} = 135{^\circ}.\]
\[\textbf{д)}\ \angle ABO = 45{^\circ};\]
\[\angle ABC = 180{^\circ} - (90{^\circ} + 45{^\circ}) =\]
\[= 45{^\circ}.\]
\[\textbf{е)}\ \angle ABC = 45{^\circ}.\]
\[\textbf{ж)}\ \angle ABC = 45{^\circ}.\]