Розв'яжіть r^2=4cos(θ)

$$r ^ { 2 } = 4 \cos ( \theta )$$

Знайдіть r

$$r=2\sqrt{\cos(\theta )}$$

$$r=-2\sqrt{\cos(\theta )}\text{, }\exists n_{1}\in \mathrm{Z}\text{ : }\left(\theta \geq 2\pi n_{1}-\frac{\pi }{2}\text{ and }\theta \leq 2\pi n_{1}+\frac{\pi }{2}\right)$$

Знайдіть θ

$$\theta =-\arccos(\frac{r^{2}}{4})+2\pi n_{1}\text{, }n_{1}\in \mathrm{Z}$$

$$\theta =\arccos(\frac{r^{2}}{4})+2\pi n_{2}\text{, }n_{2}\in \mathrm{Z}\text{, }\frac{r^{2}}{4}\leq 1\text{ and }|r|\leq 2$$