画个草图就可以解决问题了...
A B
│ /
│/
O —————C
\
\
\
D
∠AOC=90 ∠BOD=90 设∠BOC=X
∠AOB=∠AOC-∠BOC=90-X
∠AOD=∠AOC+∠COD
又∠COD=∠BOD-∠BOC
∠AOD=90+(90-X)
∠AOB:∠AOD=2:11
即 (90-X):[90+(90-X)]=2:11
解出X=70
即∠BOC=70
∠AOB=90-X=20
画个草图就可以解决问题了...
A B
│ /
│/
O —————C
\
\
\
D
∠AOC=90 ∠BOD=90 设∠BOC=X
∠AOB=∠AOC-∠BOC=90-X
∠AOD=∠AOC+∠COD
又∠COD=∠BOD-∠BOC
∠AOD=90+(90-X)
∠AOB:∠AOD=2:11
即 (90-X):[90+(90-X)]=2:11
解出X=70
即∠BOC=70
∠AOB=90-X=20