(1)三角形ABC面积 是 S= absinC/2 =√3
ab= 4
余弦定理 c^2=a^2+b^2-2*a*b*CosC
4=a²+b²-8* 1/2
a²+b²=8
a=b=2
(2)sinC+sin(B-A)=2sin2A
A=2π/3 -B
B-A= sin(2B-π/3)
sinC+sin(B-A)=2sin2A
sinπ/3 +sin(2B-π/3)= 2sin(4π/3-2B)=2sin（2B-π/3）
sin(2B-π/3）=sinπ/3
B=π/3
等边三角形 面积是 √3