√2b=a+c
由正弦定理a/sinA=b/sinB=c/sinC
等价于√2sinB=sinA+sinC
√2sin(π-A-C)=sinA+sinC
√2sin(A+C)=sinA+sinC
2√2sin[(A+C)/2]cos[(A+C)/2]=2sin[(A+C)/2]cos[(A-C)/2]
由0
√2b=a+c
由正弦定理a/sinA=b/sinB=c/sinC
等价于√2sinB=sinA+sinC
√2sin(π-A-C)=sinA+sinC
√2sin(A+C)=sinA+sinC
2√2sin[(A+C)/2]cos[(A+C)/2]=2sin[(A+C)/2]cos[(A-C)/2]
由0