sin(a+π/3)+2sin(a-π/3)-根号3cos（2π/3-a）=sinacosπ/3+cosasinπ/3+2sinacosπ/3-2cosasinπ/3-√3cosacos2π/3-√3sinasin2π/3=sina*1/2+cosa*√3/2+2sina*1/2-2cosa*√3/2-√3cosa*(-1/2)-√3sina*√3/2=-...