作函数图像：

y=√（2²-x²）

作函数图像：

y=cos(x-π/2)+cos(3x-π/2)

作函数图像：

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y=xcosxx
y=xsinx

作函数图像：

y=-2的x次方

作函数图像：

y=cosxsinx
y=cos(x+1.57)