答：
4sinAsinC-2cos(A-C)=14sinAsinC-2cosAcosC-2sinAsinC=1
2sinAsinC-2cosAcosC=1
cos(A+C)=-1/2
所以：
cosB=-cos(A+C)=1/2
所以：B=π/3
所以：A+C=2π/3
sinA+2sinC
=sin(2π/3-C)+2sinC
=(√3/2)cosC+(1/2)sinC+2sinC
=(5/2)sinC+(√3/2)cosC
=√7*[(5√7/14)sinC+(√21/14)cosC]
=√7 sin(C+t)
其中锐角t满足cost=5√7/14>0.9,sint=√21/14
所以：0