Explicație pas cu pas:
Stim ca AB=AC => ABC isoscel
ABCD parallelogram => AC=DC => ACD isoscel
mDAC=mCDA
mCDA=mADB+mCDB=3mCDB
Stim ca BD=2BC => Triunghiul DAO isoscel
Avem: mDAO=mDOA=mDAC=mCDA
mDAO+mADO+mDOA=180
3mCDB+2mCDB+3mCDB=180
8mCDB=180
mCDB=22.5
mADO=45=mADB
mADC=mABC=45+22.5=67.5 grade
2mADC+2mBAD=360
135+2mBAD=360
mBAD=mBCD=112.5 grade
