2.如圖,直線AB、CD相交于點(diǎn)O.已知∠AOC=75°,在∠AOC內(nèi)部引一條射線OE,且∠AOE=30°,請(qǐng)解答下列問(wèn)題:
(1)∠COE度數(shù)是
;∠BOC度數(shù)是
;
(2)將射線OE繞點(diǎn)O逆時(shí)針旋轉(zhuǎn)a°(0°<α<360°)到OF.
①如圖2,當(dāng)OF平分∠BOE時(shí),說(shuō)明OB平分∠DOF;
②當(dāng)∠AOF=90°時(shí),請(qǐng)求出α的度數(shù).