Posted by haifeng on 2019-12-21 20:42:39 last update 2019-12-21 20:44:26 | Answers (1) | 收藏
(a) $M_1:=\{(\cos t, \sin t)\mid t\in[0,2\pi]\}\subset\mathbb{R}^2$.
(b) $M_2:=\{(t,\sin t)\mid t\in\mathbb{R}\}\subset\mathbb{R}^2$.
References:
Klaus Hulek 著, 胥鸣伟 译 《初等代数几何》P. 16, 习题