(1) sinA sinB sinC=根号3/2(sin^2A+sin^2B-sin^2C)sinC=(√3/2)(sin^2A+sin^2B-sin^2C)/sinAsinB由正弦定理,右边转为边的形式sinC=√3(a^2+b^2-c^2)/(2ab)由余弦定理知,sinC=√3cosCtanC=√3C=π/3(2) B=π-A-C=2π...sinC=√3(a^2+b^2-c^2)/(2ab)这一步不是很懂，角化边不是会出现2R的吗正弦定理a/sinA=b/sinB=c/sinC=2Ra=2RsinA b=2RsinB c=2RsinC代入后，分子分母约去了