（1）由条件得sinB=根号7/4,b^2=ac即（sinB）^2=sinA*sinC 1/tanA+1/tanC=cosA/sinA+cosC/sinC=(cosAsinC+sinAcosC)/(sinA*sinC)=sin(A+C)/(sinA*sinC)=sinB/(sinB)^2=1/sinB=4根号7/7 （2）向量BA·向量BC=c*a*cosB=3/2,ac=2第二问是求a和c的值好吧，b^2=ac=2=(a+c)^2-2ac-2accosB=(a+c)^2-2*2-2*2*3/4==>a+c=3又ac=2所以a=1,c=2或a=2,c=1