12.8 函数图

蝴蝶图的参数方程如下

$$\begin{align} x &= \sin t \big(\mathrm e^{\cos t} - 2 \cos 4t + \sin^5(\frac{t}{12})\big) \\ y &= \cos t \big(\mathrm e^{\cos t} - 2 \cos 4t + \sin^5(\frac{t}{12})\big), t \in [- \pi, \pi] \end{align}$$