∴AD∥BC,OA=OC.
∴∠EAO=∠FCO,∠AEO=∠CFO,
在△AOE和△COF中,
{∠EAO=
The plane from Beijing to Hong Kong ________ half an hour ago.
一昼夜,时针转____ 圈,分针转____ 圈.
A.2 B.12 C.24 D.48.