如图,已知∠AOB和∠AOD的度数之比是2:11,∠AOC=∠DOB=90°,求∠AOB和∠BOC度数.

∠AOB=20,BOC=70;
AOB:AOD=AOB:(AOB+90)=2:11→(AOB+BOD)/AOB=11:2;
1+BOD/AOB=11/2
BOD:AOB=9:2
因BOD=90,则AOB=20
BOC=90-20=70