方法一：在CD上取一点E,使BE=AB=CD,则：BC=DE,△ABE是以AB、BE为腰的等腰三角形,有∠AEB=∠EAB=1/2(180°-∠B)=70°∠AED=110°,∠ACD=30°+40°=70° AC=AE.BC=DE,AC=AE,∠ACB=∠AED=110°,△ABC≌ △ADE所以,∠ADC...