已知sin(a+π/3)+sina=-4√3/5,-π/2
问题描述：
已知sin(a+π/3)+sina=-4√3/5,-π/2
答
sin(a+π/3)+sina=-4√3/5sinacosπ/3+cosasinπ/3+sina=-4√3/5(3/2)sina+(√3/2)cosa=-4√3/5sina=(2/3)*(-4√3/5-√3/2*cosa)=-(8√3/15+√3/3*cosa)代入(sina)^2+(cosa)^2=1令x=cosa[-(8√3/15+√3/3*x)]^2+x^2=...