\[\angle AOB = 90^{о} - прямой;\ \ \]
\[\angle AOD = 74^{о};\ \ \angle BOC = 66^{о}.\]
\[\angle AOC = \angle AOB - \angle BOC = 90^{о} - 66^{о} = 24^{о}.\]
\[\angle COD = \angle AOD - \angle AOC = 74^{о} - 24^{о} = 50^{о}.\]
\[Ответ:50^{о}\text{.\ }\]