小古6024
幼苗
共回答了15个问题 举报
设a/sinA = b/sinB = c/sinC = k
则 a=ksinA,b=ksinB,c=ksinC
则 b+c=sqrt(3)*a -> sinB+sinC = sqrt(3)*sinA
而 A+B+C=180 A=60
则 sinB+sin(120-B)=3/2
则 sinB + sqrt(3)/2*cosB -1/2*sinB = sqrt(3)* sin(B+30) = 3/2
sin(B+30) = sqrt(3)/2
1年前
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