cotC/cotB=cosCsinB/(cosBsinC).所以2a/c=1+cosCsinB/(cosBsinC)=(cosCsinB+cosBsinC)/(cosBsinC)=sin(B+C)/(cosBsinC)=sinA/(sinCcosB)=a/(c*cosB)所以得到cosB=1/2.B=60°(√3+1)/2=c/a=sinC/sinA=sin(120°-A)/si...