Question

ABC中∠ABC=50°∠ACB=80°延长CB至D,使DB=BA,延长BC至E,使CE=CA.连接AD,AE.求∠D,

Answer 1

因为,AB=BD,∠ABC=50°

所以,∠D=∠BAD= (1/2)*∠ABC = 25°

同理,∠E=∠CAE= (1/2)*∠ACB = 40°

所以,∠DAE=180°-∠D-∠E = 180°-25°-40°=115°