（1）當(dāng)x=π/18時(shí),y=0,
當(dāng)x=2π/9時(shí),y=1,
當(dāng)x=π/3時(shí),y=0,
當(dāng)x=5π/9時(shí),y=-1,
當(dāng)x=2π/3時(shí),y=0,
∴圖像如下：

（2）當(dāng)x=-π/2時(shí),y=0
當(dāng)x=π時(shí),y=1,
當(dāng)x=5π/2時(shí),y=0,
當(dāng) x=4π時(shí),y=-1,
當(dāng)x=11π/2時(shí),y=0,
圖像如下：