$$ \vec{r}(t) = \langle 2,1,1 \rangle + t\langle 1,3,3 \rangle, \quad t \in [0, 1] $$
$$ \vec{r}(t) = P + \cos(t)\vec{e_1} + \sin(t)\vec{e_2}, \quad t \in [0, 2\pi] $$
$$ \vec{r}(t) = \langle \cos(4t), \sin(4t), t/2 \rangle, \quad t \in [0, 2\pi] $$
$$ \text{Trébol: } \vec{r}(t) = \langle \sin(t)+2\sin(2t), \cos(t)-2\cos(2t), -\sin(3t) \rangle $$
$$ \text{Cúbica Torcida: } \vec{r}(t) = \langle t, t^2, t^3 \rangle, \quad t \in [-1.5, 1.5] $$