下列地点符合“北半球”、“中纬度”二个条件是( )
A:10°N,180°
B:45°N,105°W
C:35°S,10°W
D:65°N,105°E
关于四幅图中阴影地区特征的叙述,正确的是 ( )
如图,AB是⊙O的直径,点F,C是⊙O上两点,且AF∧=FC∧=CB∧,连接AC,AF,过点C作CD⊥AF交AF延长线于点D,垂足为D.
(1)求证:CD是⊙O的切线;
(2)若CD=23,求⊙O的半径.
The twin brothers often put the same present in stocking(袜子)on Christmas Day.