1. **State the problem:** Convert the Cartesian point $(-1, -2)$ to polar coordinates $(r, \theta)$, where $r = \sqrt{5}$ and $0 \leq \theta < 2\pi$.
2. **Formula used:**
Polar coordinates are given by:
$$r = \sqrt{x^2 + y^2}$$
$$\theta = \arctan\left(\frac{y}{x}\right)$$
Important: Adjust $\theta$ based on the quadrant of the point.
3. **Calculate $r$ to verify:**
$$r = \sqrt{(-1)^2 + (-2)^2} = \sqrt{1 + 4} = \sqrt{5}$$
This matches the given $r$.
4. **Calculate $\theta$:**
$$\theta = \arctan\left(\frac{-2}{-1}\right) = \arctan(2)$$
5. **Determine the quadrant:**
The point $(-1, -2)$ is in the third quadrant (both $x$ and $y$ negative).
6. **Adjust $\theta$ for third quadrant:**
Since $\arctan(2)$ gives an angle in the first quadrant, add $\pi$ to get the correct angle:
$$\theta = \arctan(2) + \pi$$
7. **Final polar coordinates:**
$$\boxed{\left(\sqrt{5}, \arctan(2) + \pi\right)}$$
This means the radius is $\sqrt{5}$ and the angle $\theta$ is $\arctan(2) + \pi$, which lies between $\pi$ and $2\pi$ as required.
Polar Conversion 5D9Bd0
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