在平行四边形ABCD中,点E在边AB上,且AE∶EB=1∶2,DE与AC交于点F,若△AEF的面积为6 cm2,则△ABC的面积为______ cm2.
如图所示,AB为⊙O直径,CD切⊙O于D,AB延长线交CD于点C,若∠CAD=25°,则∠C为
A.45° B.40°
C.35° D.30°
如图所示,四边形ABCD是⊙O的内接四边形,延长BC到E,已知∠BCD∶∠ECD=3∶2,那么∠BOD等于
A.120° B.136°
C.144° D.150°
如图,AB为⊙O直径,MN切⊙O于C,AC=BC,则sin∠MCA=
A. B.
C. D.
如图所示,CD切⊙O于B,CO的延长线交⊙O于A,若∠C=36°,则∠ABD的度数是
A.72° B.63°
C.54° D.36°
如图所示,AC切⊙O于D,AO的延长线交⊙O于B,且AB⊥BC,若AD∶AC=1∶2,则AO∶OB=
A.2∶1 B.1∶1
C.1∶2 D.1∶1.5