Question

如图,已知直线AB和CD相交于点O,OM平分∠BOD,ON⊥OM,∠AOC=70°

Answer 1

题里是OM平分∠BOD,而图是OE平分∠BOD,这里E看成以M为主

∠DOB＝∠AOC＝70°

OM平分∠DOB,则∠DOM＝∠BOM＝70/2＝35°

ON垂直OM,则∠NOM＝90°

∠AON＝180° - ∠BON - ∠NOM＝180° - 35° - 90°＝55°

∠DON的余角是：90° - ∠DOM＝90° - 35°＝55°