平面几何图形

摆线

$$\{\begin{array}{l}x=a(t-\sin t)\\ y=a(1-\cos t)\end{array}$$

心型线

$$r=\{\begin{array}{l}a(1-\cos \theta )\\ a(1+\cos \theta )\\ a(1-\sin \theta )\\ a(1+\sin \theta )\end{array}$$

双扭线

$$r^2=\{\begin{array}{l}{a}^2\cos 2\theta \\ a^2\sin 2\theta \end{array}$$

螺线

$$r=\{\begin{array}{l}a\theta \\ e^{a\theta }\\ \frac{a}{\theta }\end{array}$$

玫瑰线

$$r=\{\begin{array}{ll}a\sin \theta & \text{偏心圆}\\ a\cos \theta & \text{偏心圆}\\ a\sin 2\theta & \text{四叶玫瑰线}\\ a\cos 2\theta & \text{四叶玫瑰线}\\ a\sin 3\theta & \text{三叶玫瑰线}\\ a\cos 3\theta & \text{三叶玫瑰线}\end{array}$$

星形线

$$\{\begin{array}{l}x=a{\cos }^{3}t\\ y=a{\sin }^{3}t\end{array}\text{or}{x}^{\frac{2}{3}}+y^{\frac{2}{3}}=a^{\frac{2}{3}}$$

直线

$$\{\begin{array}{l}x=a{\cos }^{2}t\\ y=a{\sin }^{2}t\end{array}\text{or}{x}^1+y^1=a^1$$

圆

$$\{\begin{array}{l}x=a{\cos }^{1}t\\ y=a{\sin }^{1}t\end{array}\text{or}{x}^2+y^2=a^2$$

一个图形（欧几里得26·11月模考）

$$\{\begin{array}{l}x=a{\cos }^{\frac{2}{3}}t\\ y=a{\sin }^{\frac{2}{3}}t\end{array}\text{or}{x}^3+y^3=a^3$$