AC上取一点E,使AE=AB
∵AB+BD=AC AE+CE=AC∴BD=CE
∵AB=AE,∠BAD=∠EAD,AD=AD
∵△ABD≌△AED ∴BD=ED ∠B=∠AED
∴CE=ED
∠C=∠EDC
∵∠C+∠EDC=∠AED
2∠C=∠AED
∴2∠C=∠B
角B:∠C=2:1
AC上取一点E,使AE=AB
∵AB+BD=AC AE+CE=AC∴BD=CE
∵AB=AE,∠BAD=∠EAD,AD=AD
∵△ABD≌△AED ∴BD=ED ∠B=∠AED
∴CE=ED
∠C=∠EDC
∵∠C+∠EDC=∠AED
2∠C=∠AED
∴2∠C=∠B
角B:∠C=2:1