△ABC中∵sin(B+A)=2sin(B+C)∴sinC=2sinA为什么?

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△ABC中∵sin(B+A)=2sin(B+C)∴sinC=2sinA为什么?△ABC中∵sin(B+A)=2sin(B+C)∴sinC=2sinA为什么?△ABC中∵sin(B+A)=2sin(B+

△ABC中∵sin(B+A)=2sin(B+C)∴sinC=2sinA为什么?
△ABC中∵sin(B+A)=2sin(B+C)∴sinC=2sinA为什么?

△ABC中∵sin(B+A)=2sin(B+C)∴sinC=2sinA为什么?
∵B+A+C=π
sin(B+A)=2sin(B+C)
∴sin(B+A)=sin(π-C)=sinC
2sin(B+C)=2sin(π-A)=2sinA
∴sinC=2sinA