cos(3π/2 +α)=sinα cos(3π/2 -α)=-sinα 奇变偶不变，符号看象限
宸茬煡鍚戦噺=(2cos蠅x锛�-1)锛� =(sin蠅x-cos蠅x锛�2)锛屽嚱鏁癴(x)= 路+3鐨勫懆鏈熶负蟺銆�锛�2锛� 鑻ュ嚱鏁癴(x)鐨勫浘鍍忓