cos²（50°+α）+cos²（40°-α）-tan(30°-α)tan(60°+α)=? 你的题是这个吗?如果是就是这样的tan(30°-α)=cot[90°-(30°-α)]=cot(60°+α)tan(30°-α)tan(60°+α)=cot(60°+α)tan(60°+α)=1同理...