a：b:c=3:根号7:2则设a=3t,b=√7t,c=2t则a>b>c即A>B>C利用余弦定理cosB=(a²+c²-b²)/(2ac)=(9t²+4t²-7t²)/(2*3t*2t)=1/2∴ B=60°∴ A+C=120°,即最大角最小角的和是120°...