$$\begin{aligned}
r&=0.3\theta,\quad \theta\in[0,4\pi]\\
\vec r(\theta)&=(0.3\theta\cos\theta,\;0.3\theta\operatorname{sen}\theta)
\end{aligned}$$
$$\begin{aligned}
r&=2(1+\cos\theta),\quad \theta\in[0,2\pi]\\
\vec r(\theta)&=(2(1+\cos\theta)\cos\theta,\;2(1+\cos\theta)\operatorname{sen}\theta)
\end{aligned}$$
$$\begin{aligned}
r&=3\operatorname{sen}(3\theta),\quad \theta\in[0,\pi]\\
\vec r(\theta)&=(3\operatorname{sen}(3\theta)\cos\theta,\;3\operatorname{sen}(3\theta)\operatorname{sen}\theta)
\end{aligned}$$
$$\begin{aligned}
r&=2\sqrt{\cos(2\theta)},\quad \theta\in\left[-\frac{\pi}{4},\frac{5\pi}{4}\right]\\
\vec r(\theta)&=(2\sqrt{\cos(2\theta)}\cos\theta,\;2\sqrt{\cos(2\theta)}\operatorname{sen}\theta)
\end{aligned}$$