如图,⊙O内切于△ABC,切点为D、E、F,∠B=45°,∠C=55°,连接OE、OF、OE、OF,则∠EDF等于( )
A:45°
B:55°
C:50°
D:70°
下列工程中,属于战国时期秦国修筑的有( )
①都江堰 ②郑国渠
③万里长城 ④灵渠
如图,已知BC为⊙O的直径,BA平分∠FBC交⊙O于点A,D是射线BF上的一点,且满足BDBA=BABC,过点O作OM⊥AC于点E,交⊙O于点M,连接BM,AM.
All of us have been to the park ____________________ because both of you are ill at home.