Răspuns:
4. Raspunsul este 105°
AC=BC&mACB=80°=> ∆BAC-isoscel in a, deci mCAB=(180°-80°)/2=50°, AS bis=> mCAS=25° AS||CD, AC-secanta=> mCAS=mACD=25°
mBCD=mACB+mACD=25°+80°=105°
5. Raspunsul este 105°
∆ACB-drpt. isoscel in A=> mACB=(180°-90°)/2=45°
CD=AC/2, ∆ADC-drpt in D=> Prin reciproca teoremei unghiului de 30° => mDAC=30°
mDCA=180-90-30=60°
mBCD=60°+45°=105°
