三角函数加法定理
(1) $$\sin(x ± y)=\sin(x) \cdot \cos(y) ± \cos(x) \sin(y) $$
(2)$$ cos(x \pm y) = cos(x)\cdot \cos(y) - \sin(x)\cdot \sin(y)$$
(1) $$\sin(x ± y)=\sin(x) \cdot \cos(y) ± \cos(x) \sin(y) $$
(2)$$ cos(x \pm y) = cos(x)\cdot \cos(y) - \sin(x)\cdot \sin(y)$$