30min内发答案分数双倍啊在三角形ABC中,已知sinA=2sinBcosC,asinA=bcosB,求A,B,C

30min内发答案分数双倍啊
在三角形ABC中,已知sinA=2sinBcosC,asinA=bcosB,求A,B,C

sinA=sin(B+C)=sinBcosC+cosBsinC=2sinBcosC
sinBcosC-cosBsinC=0=sin(B-C)
B=C
asinA=bcosB
a(sinBcosC+cosBsinC)=bcosB
2asinBcosB=bcosB
2asinB=b
sinA=1/2,A=30,150
B=C=75,15