∵ A+B=120º∴C=180º-(A+B)=60º∵c=3根据正弦定理2R=c/sinC=3/(√3/2)=2√3∴sinA=a/(2R)=a/(2√3)sinB=b/(2R)=b/(2√3)∵SinA+SinB=2√6•sinA•sinB ∴(a+b)/(2√3)=2√6*ab/12∴a+b=√2...