1.3 Èý½Çº¯ÊýµÄÓÕµ¼¹«Ê½

https://baike.baidu.com/item/%E4%B8%89%E8%A7%92%E5%87%BD%E6%95%B0%E5%85%AC%E5%BC%8F/4374733 ¹«Ê½¶þ $\sin (\pi+\alpha ) = -\sin a$ $\cos (\pi+a) = -\cos a