1) ΔBAD-равносторонний⇒ ∠BAD=∠ABD=∠BDA=60°
2) ∠BDC=180-∠BDA ∠BDC=180-60= 120
DC=AD=DB ⇒ ∠BDC=∠DCB ⇒ ∠BDC+∠DCB= 180-120= 60
∠DCB=60÷2=30°
O: 120° 30° 30°
1) ΔBAD-равносторонний⇒ ∠BAD=∠ABD=∠BDA=60°
2) ∠BDC=180-∠BDA ∠BDC=180-60= 120
DC=AD=DB ⇒ ∠BDC=∠DCB ⇒ ∠BDC+∠DCB= 180-120= 60
∠DCB=60÷2=30°
O: 120° 30° 30°