sinb(sinacosc+cosasinc)=sinasinc sinbsin(a+c)=sinasincsinbsinb=sinasinc由正弦定理得b^2=ac=2cosb=(a^2+c^2-b^2)/2ac=3/4sinb=根号7/4S=acsinb/2=根号7/4
你这题没打全吧
