Question

1,.如图.已知∠BOC＝2∠AOB,OD平分∠AOC,∠BOD＝14°,求∠AOB的度数

Answer 1

设∠AOB的度数为x,则∠BOC=2∠AOB=2x,

∠AOC=∠AOB+∠BOC=3x,因OD平分∠AOC,

则∠AOD=∠AOC/2=3x/2,又∠AOD-∠AOB=∠BOD,

则3x/2-x=14,解得x=28°

2、选C.

分析：△GFE由△GCF对折得到,故∠CFG=∠EFG=∠CFE/2

因FH平分∠BFE,故∠HFE=∠BFE/2

∠GFH=∠EFG+∠HFE=∠CFE/2+∠BFE/2=(∠CFE+∠BFE)/2=90°