a) $\widehat{BOD}=180^{\circ}-97^{\circ}=83^{\circ}; \widehat{DOE}=97^{\circ}-56^{\circ}=41^{\circ};\widehat{COE}= 180^{\circ}-56^{\circ}-42^{\circ}=82^{\circ}$
b) $\widehat{COD}=83^{\circ}-42^{\circ}=41^{\circ};\widehat{DOE}=97^{\circ}-56^{\circ}=41^{\circ}$
Vậy OD là tia phân giác góc COE